2022-08

Journal of Molecular Liquids (Issue : 12) (Volume : 279)

Various fluids are implemented for mass/heat transfer procedures in industrial applications. These structures' behavior inside the metallic nanochannels (NCs) in the presence of the obstacle was described. To this end, the Molecular Dynamics Simulation (MDS) method is performed by the LAMMPS package. The various atomic forces in defined structures are defined using Universal Force Field (UFF) and Embedded Atom Model (EAM). In addition, physical parameters such as temperature (T), potential energy (PE), Radial Distribution Function (RDF), profiles of density (D)/velocity(V)/T, position histogram, trajectory lines, and interaction energy are reported for nanofluid (NF) behavior description. MDS results display the equilibrium of Ar (as fluid) and Pt (as NC) in the presence of obstacles after t=20 ns. Also, our simulations predict that the obstacles increase/decrease the average values of fluid adsorption/mobility inside the NC.

2022-08

Case Studies in Thermal Engineering (Issue : 13) (Volume : 169)

The boiling process is an efficient and effective transfer of heat. Generally, different parameters such as temperature, pressure, external forces, etc., amend the nanofluid's pool boiling heat transfer (PBHT) rate. The present article uses molecular dynamics (MD) simulation to study the efficacy of different external forces(Efs) and heat fluxes (HF) on the atomic and PBHT of water/Fe nanofluid (NF). This study is performed in a microchannel (MC) with Fe-walls. The atomic behavior of the simulated structure is examined using the change in maximum temperature (T), velocity(v), and density(D), and the PBHT is studied by the phase change time (PCT) and HF. Results show that the maximum of the T, V, and D increase with increasing the EF and heat flux. Numerically, with increasing EF from 0.001 to 0.005 eV/Å, the maximum od D, maximum of V, and maximum of T increase from 0.033 atom/Å3, 0.038 Å/fs, and 789 K to 0.034 atom/Å3, 0.039 Å/fs, and 900 K, respectively. Also, the result appears that the transferred HF increases by improving the applied EF, and the PCT reduces from 0.33 to 0.32 ns. So, the PBHT in the NF is improved with increasing EF. On the other hand, the increase in external HF led to a reduction in the PCT (from 0.33 to 0.21 ns).

2022-07

Case Studies in Thermal Engineering (Issue : 1) (Volume : 37)

Due to the importance and efficiency of heat transfer in industrial equipment, studying refrigerants to improve their efficiency in heating or cooling was attracted much attention. In this paper, the molecular dynamics (MD) simulation is employed to study the refrigerant heat transfer capability inside an nanochannel. The thermal performance of simulated samples is examined by changing the heat flux (HF) and thermal conductivity (TC). The results reveal that after 10 ns, the TCs of the oils based on ester and hydrocracked were reached to 0.14 and 0.33 W/m.K, and the HFs were reached to 511 and 793 W/m2, respectively. The obtained results indicate a better thermal behavior for hydrocracked oil, which can also transfer more heat. Therefore, the hydrocracked was chosen as the based oil for the rest of the research. On the other hand, different percentages of Cu and Fe3O4 hybrid nanoparticles and carbon nanotubes are added to the hydrocracked oil. By increasing the nanoparticles’ percentage from 1 to 4%, the HF increases from 792 to 911 W/m2, and the TC also raises from 0.40 to 0.52 W/m.K. According to the results, adding the hybrid nanoparticles into the oil sample improves its thermal behavior. It is hoped that the obtained results in this research can be useful and applicable in the industry fields.

2022-07

Journal of Energy Storage (Issue : 1) (Volume : 54)

In recent years, due to increasing energy requirements and special attention to the issue of carbon, hydrogen fuel has become an efficient alternative to energy carriers. The aim of this article is to present and investigate of a novel solar-driven hydrogen generation process. The introduced hybrid energy system (HES) is comprised of a solid oxide electrolyzer (SOE), solar photovoltaic (SPV) modules, and solar dish collectors (SDCs). Further, since one of the most attractive utilizations of hydrogen fuel is as a fuel cell's fuel, the present HES suggests that hydrogen fuel be injected into molten carbonate fuel cell (MCFC) to convert it into useful electrical and thermal energies. Finally, the electrical energy obtained from HES is stored via a relatively new hybrid storage system (i. e., pumped hydro and compressed air (PHCA) storage system) for peak and night hours. Therefore, the considered HES in the present study can generate electrical and thermal power, hydrogen fuel and oxygen gas, and store electricity. Although some publications on solar-driven hydrogen generation process are available, there is no study on proposed HES of the present article that considers both energy production and storage. In other words, the components embedded in the proposed HES are developed in such a way that the relationships between them are novel. According to the numerical simulation, it was found that the electrical energy production rate and electrical efficiency of HES are almost 183.1 kWh/day and 33.6 %, respectively. HES can also produce approximately 3.9 kg of hydrogen fuel per day. Moreover, the storage system size for storing the electricity yielded from the considered HES should be nearly 29.9 m3 (at n = 1.2). Also, the storage efficiency of the energy cycle is 59.1 %. The considered process is investigated under different effective parameters in order to identify their effectiveness.

2022-07

Journal of Molecular Liquids (Issue : 10) (Volume : 363)

Nanochannels (NCs) are structures for mass transfer (MT) and heat transfer (HT) procedures in actual usages. Prior reports display the atomic behavior of various fluids inside perfect NCs. This study uses the molecular dynamics simulation (MDS) to examine the impact of number of obstacles (N.Os) on argon flow inside Platinum NCs. Simulation outputs are presented by calculating the physical quantities such as temperature (T), potential energy (PE), density (D)/temperature (T)/velocity (V) profiles, and interaction energy (IE). MDS results show that as the N.O increases, the maximum density increases from 0.093 to 0.099 atom/Å3. The maximum velocity decreases from 0.0031 to 0.0025 Å/ps by increasing the N.Os. The maximum temperature decreases from 329.46 to 318.43 K. By increasing the N.Os, the fluid particles' oscillations (FP) and their temperature also decrease. This mechanism can reduce the temperature in the HT process. In addition, with increasing the N.Oss from 1 to 4, the IE increases from −60.52 to -70.86 eV. This increase in IE can reduce the atomic stability of NCs. This behavior reduces the lifetime of NCs in heat/mass transfer processes. Therefore, it is expected that with the outcomes of the current examination and the control of the N.Os, we can optimize the various processes like MT and HT for industrial purposes.

2022-05

Journal of Thermal Science (Issue : 1) (Volume : 43)

Because the rotational current stabilizes the flame by creating a recirculation zone, it may increase the risk of reversal. For this reason, low-spin combustion is used to stabilize the flame while preventing flashbacks. Therefore, in this study, the combustion flow of methane gas in a low-swirl burner is simulated using a partially premixed combustion model. Furthermore, the fuel flow rate is considered constant. The research parameters include swirl angle (θ=35°–47°), equivalence ratio (φ=0.6–0.9) and inlet axial flow radius (R=0.6–0.7) and effect of these parameters on temperature distribution, flame length, flame rise length, velocity field, and streamlines of the number of pollutant species are investigated. The contours of streamline, temperature distribution, and velocity distribution are also presented for analysis of flow physics. The results show that with increasing the fuel-air ratio, the strength of the axial flow decreases, and the position of the maximum flame temperature shifts toward the inlet of the reactants. The results also reveal that by increasing the swirl angle of the flow, the position of the minimum velocity value (opposite to the direction of the axis) tends towards the outlet. The results also indicate that the maximum temperature of the combustion chamber increases with increasing the swirl angle, and in θ=35°, the maximum temperature is 1711°C and in θ=41°, this value is 1812°C. Finally, by increasing the swirl angle to θ=47°, the maximum flame temperature position is found at a considerable distance from the inlet and is 1842°C.

2022-04

Chinese Journal of Chemical Engineering (Issue : 4) (Volume : 44)

Heat exchangers are integral parts of important industrial units such as petrochemicals, medicine and power plants. Due to the importance of systems energy consumption, different modifications have been applied on heat exchangers in terms of size and structure. In this study, a novel heat exchanger with helically grooved annulus shell and helically coiled tube was investigated by numerical simulation. Helically grooves with the same pitch of the helical coil tube and different depth are created on the inner and outer wall of annulus shell to improve the thermal performance of heat exchanger. In the first section, thermal performance of the shell and coil heat exchanger with the helical grooves on its outer shell wall was compared with same but without helical grooves. At the second section, helically grooves created on both outer and inner wall of the annulus shell with different groove depths. The results showed that the heat exchanger with grooves on both inner and outer shell wall has better thermal performance up to 20% compared to the heat exchanger with grooves on only outer shell wall. The highest thermal performance achieves at lower flow rates and higher groove depths whereas the pressure drop did not increase significantly.

2022-02

Chinese Journal of Chemical Engineering (Issue : 1) (Volume : 42)

In current numerical study, forced flow and heat transfer of water/NDG (Nitrogen-doped graphene) nanofluid in nanoparticles mass fractions (u) of 0, 2% and 4% at Reynolds numbers (Re) of 10, 50, 100 and 150 are simulated in steady states. Studied geometry is a two-dimensional microchannel under the influence of nanofluid jet injection. Temperature of inlet fluid equals with Tc = 293 K and hot source of microchannel is under the influence of oscillating heat flux. Also, in this research, the effect of the variations of attack angle of triangular rib (15
, 30
, 45
and 60
) on laminar nanofluid flow behavior inside the studied rectangular geometry with the ratio of L/H = 28 and nanofluid jet injection is investigated. Obtained results indicate that the increase of Reynolds number, nanoparticles mass fraction and attack angle of rib leads to the increase of pressure drop. By increasing fluid viscosity, momentum depreciation of fluid in collusion with microchannel surfaces enhances. Also, the increase of attack angle of rib at higher Reynolds numbers has a great effect on this coefficient. At low Reynolds numbers, due to slow motion of fluid, variations of attack angle of rib, especially in angles of 30
, 45
and 60
are almost similar. By increasing fluid velocity, the effect of the variations of attack angle on pressure drop becomes significant and pressure drop figures act differently. In general, by using heat transfer enhancement methods in studied geometry, heat transfer increases almost 25 %.

2021-10

scientific reports (Issue : 11) (Volume : 252)

In the present study, the improvement of mechanical properties of conventional concretes using carbon nanoparticles is investigated. More precisely, carbon nanotubes are added to a pristine concrete matrix, and the mechanical properties of the resulting structure are investigated using the molecular dynamics (MD) method. Some parameters such as the mechanical behavior of the concrete matrix structure, the validation of the computational method, and the mechanical behavior of the concrete matrix structure with carbon nanotube are also examined. Also, physical quantities such as a stress–strain diagram, Poisson’s coefficient, Young’s modulus, and final strength are calculated and reported for atomic samples under external tension. From a numerical point of view, the quantities of Young’s modulus and final strength are converged to 35 GPa and 35.38 MPa after the completion of computer simulations. This indicates the appropriate effect of carbon nanotubes in improving the mechanical behavior of concrete and the efficiency of molecular dynamics method in expressing the mechanical behavior of atomic structures such as concrete, carbon nanotubes and composite structures derived from raw materials is expressed that can be considered in industrial and construction cases.

2021-07

Case Studies in Thermal Engineering (Issue : 4) (Volume : 27)

Prediction the thermal conductivity of nanofluids has been subject of many researches. Artificial Neural Networks are used to obtain thermal conductivity of NAnofluids because not only this method is fast and acurate but also it can reduce the Lab costs. To predict the thermal conductivity of water- EG/MWCNT-Al2O3 hybrid nanofluid () a feed-forward neural network with different neuron numbers has been tested and the best network based on the performance is selected. The Levenberg Marquardt algorithm is used for training the network, which is one of the best algorithms in machine learning. Also, using a fitting method, a surface is used to illustrate the behavior of nanofluids based on the volume fraction of nanoparticles () and temperature (T). 0, 0.001, 0.002, 0.004, 0.008, 0.0016 and T = 25, 30, 35, 40, 45, 50 °C are used.. The obtained results show that the ANN and Fitting results are close to the experimental datapoints, and both methods can predict accurately. As the results of these methods are very close, but the ANN method is better in predicting the behavior of this nanofluid.

2021-07

International Communications in Heat and Mass Transfer (Issue : 7) (Volume : 126)

In this research, the molecular dynamics simulation method is employed to simulate the boiling flow of argon flow inside the microchannels with different surfaces of ideal and roughened with cone barriers, cubic barriers, and spherical barriers respectively. For all simulations, boundary walls of all microchannels are set at a temperature of 98 K to prepare the required thermal energy for boiling argon fluid flow within channels. Also, to enforce argon fluid to flow along the mentioned microchannels, a unique external driving force is prepared at the entry region of all microchannels. Afterward, the evolution of boiling flow is reported in four-time steps of 250,000, 500,000, 750,000, and 1,000,000, respectively. Then, velocity and temperature profiles of argon flow are reported after completion of the boiling process at 1000000-time steps. Investigations in the progress of boiling flow until 7,500,000-time steps show different …

2021-07

Energy Reports (Issue : 2) (Volume : 7)

Abstract SCPP (Solar Chimney Power Plant) parameters were investigated and modified by using Computational Fluid Dynamics (CFD). In this study, the hydrodynamic parameters of flow and heat transfer in an SCPP were numerically investigated. The main purpose of this research is to investigate the effect of geometrical parameters and different thermal boundary conditions on the performance of SCPP in a two-dimensional space. In this research, the effect of parameters such as heat flux (200, 400, 600, and 800 Wm− 2), collector radius (100, 120, 140, and 160 m), and divergent angle (0° to 3°) of the chimney was considered. The height of the inlet section and the height of the chimney are constant and equal to 1.7 m and 195 m, respectively. By increasing the divergent angle of SCh θ= 1∘, the rate of power generation improvement of the turbine is reduced. Therefore, the radius of SC and solar radiation has a …

2021-07

Journal of Molecular Liquids (Issue : 9) (Volume : 338)

Due to the increasing development of nanotechnology and its wide applications, the flow of a nanofluid in a duct is also optimal geometric construction of ducts in the fabrication and production of various ducts to increase efficiency in nanofluid behavior are essential. In this paper, by using the molecular dynamics (MD) simulation process, the effect of Fe3O4 nanoparticles on the behavior of water-based fluid is investigated. Physical parameters such as total temperature, potential energy, fluid, nanofluid density profiles, fluid velocity, nanofluid profiles, and fluid and nanofluid temperature profiles are reported. Also, the effect of the number of layers and wall material on fluid flow is investigated. Therefore, the channel wall material in the following simulations will be considered as platinum, copper, and iron. Over time, the temperature of atomic structures reaches 300 K, which indicates the temperature stability in the simulated atomic structures. The results show that by increasing the number of wall layers in nanochannels and similar microchannels, interactions between fluid particles and walls increase. As these interactions increase, the accumulation of fluid particles in the vicinity of the channel walls increases, which increases the density of the shelves adjacent to the channel walls. Also, by changing the microchannel material from copper to iron and platinum, the number of interactions between particles in the present structures increases. This increase in the number of interactions between the particles present in the microchannel wall and the base fluid causes the maximum density to be observed in the platinum microchannel.

2021-06

Case Studies in Thermal Engineering (Issue : 4) (Volume : 26)

This paper aims to determine the thermal conductivity (knf) of oxide of tungsten (WO3)-MWCNTs/hybrid engine oil, through an Artificial Neural Network (ANN). Nanofluid were prepared by the suspension of nanoparticles in engine oil. The experiments were conducted at a volume fraction of nanoparticles φ = 0.05 to φ = 0.6%, as well as a temperature range of T = 20°C–60 °C. The ANN was then used to estimate the knf, and the optimum neuron number was 7. Results showed that the absolute error values of the ANN method in many points are zero. Also, the ANN had smaller error values compared to the correlation method. ANN showed acceptable performance and correlation coefficient. Also, a correlation method was used to predict knf.

2021-06

Journal of Molecular Liquids (Issue : 7) (Volume : 338)

In this work, molecular dynamics simulation of boiling flow of argon fluid is presented inside microchannels with ideal and roughened surfaces. In the first step, fluid flow is simulated inside ideal microchannels. Then, roughness elements with cone, cubic, and spherical shapes are simulated on the surfaces ofideal microchannels. Boundary conditions are unique to get comparable results in density, velocity, and temperature profiles. Results of density profiles are reported at four-time steps of 250000, 500000, 750000, and 1000000, respectively. Next, velocity and temperature profiles are presented at 1000000-time steps. It was reported that density distribution in the 300 layers in the center of a microchannel with cubic barriers commences at initial time steps while other microchannels begin in higher time steps. But, with the progress of boiling flow, central layers of a rough microchannel with cubic barriers have lower density values than those of other microchannels. On the other side, quantitative results indicate that density differences in the central regions of microchannels are compensated with increasing time steps. Therefore, it is concluded that the shape of barriers is important and reasonable to bother normal distribution of atoms within different regions of microchannels.

2021-06

Journal of Molecular Liquids (Issue : 10) (Volume : 339)

The carbon nanotubes are among the most robust materials known to main (both in terms of tensile strength and vibrational properties). This strength is derived from the covalent bonds between carbon particles. In this research, carbon nanotubes in different sizes and chiralities and argon flow at supersonic velocity are simulated with molecular dynamics simulations, and their mechanical behavior is investigated. In this study, the stability of atomic structures, the effect of temperature and pressure on carbon nanotubes' vibrational behavior, and the effect of the velocity of argon atoms (ultrasonic flow) on the vibrational behavior of carbon nanotubes were investigated. Numerically, as the temperature and pressure of the simulated samples increase, the numerical value of the oscillation amplitude decreases to 2.12 Å and 2.30 Å, respectively. Also, with increasing temperature and pressure, these structures' frequency value rises to the numerical value of 13.02 ps−1 and 12.59 ps−1, respectively.

2021-05

Energy Reports (Issue : 1) (Volume : 7)

The liquid desiccant air conditioning system is amongst the promising technologies for the provision of efficient air conditioning, particularly in hot humid climate conditions. By their benefits, membrane-based dehumidification systems have drawn large attention. Various techniques are used to enhance the performance of different dehumidification system types. The effect of using calcium chloride nanofluid solution with the added silicate nanoparticles as a desiccant solution in a hollow fiber membrane contactor system investigated experimentally. The airflow rate through the fibers is 11.2 m3/h with inlet relative humidity and temperature of 60 % and 35 °C, respectively. The sensitivity analysis was made to reveal the effect of desiccant temperatures, nanoparticle concentrations, and solution flow rates on sensible, latent, and total effectiveness and 2nd law efficiency of the system. The results indicate that using nanofluid instead of a pure desiccant solution, the values of sensible and latent effectiveness improved at the condition of high inlet solution temperature. The effect of employing nanofluid on exergy performance is the highest for the highest concentration of nanoparticles and inlet solution temperature. The maximum change of exergy destruction rate resulted by using nanofluid solution took place at a maximum flow rate of 244 ml/min for 1% nanofluid concentration. Using 1 % nanofluid instead of a pure solution, the rate of exergy destruction increased by 82 % and 160 % for 20 °C and 26 °C solution temperatures, respectively.

2021-04

Mathematics and Computers in Simulation (Issue : 2021) (Volume : 188)

Computational hemodynamics (CHD) is a promising engineering technique that has allowed doctors to learn a lot about patients’ conditions in various diseases such as cardiovascular disease (CVD) and even surgery. In industrialized countries, hypertension is becoming a widespread public health issue, resulting in death in extreme cases. A successful method for investigating hypertension in both diastolic and systolic conditions is to use the finite volume method (FVM) to incorporate velocity and pressure. Due to the use of Magnetic Resonance Image (MRI) and Digital Imaging and Communications in Medicine (DICOM), the 3D geometry has an acceptable accuracy, and the geometry has been created based thereon. The flow of blood is regarded as steady, lamina, incompressible, and non-Newtonian. Herein, all the age groups have their unique effect on the parameters reported, including Nusselt number and dimensionless numbers, e.g., average wall shear stress (AWSS), temperature, and pressure drop. In such a numerical simulation, all the results revealed that the parameters improved by increasing diastolic and systolic blood pressure. Nevertheless, the patient is recommended to see a doctor urgently in case of a hypertensive situation.

2021-04

Environment Development and Sustainability (Issue : 1) (Volume : 27)

In this study, heat transfer and airfield around a parabolic trough solar collector are simulated. The effect of the pitch angle, two-axis tracking system, and wind speed on the collector thermal performance is evaluated. Three-dimensional and turbulent flow equations are used. Simulations are performed at noon, for the 45th day of summer, for the geographical location of Isfahan. The effects of wind velocities from V = 1 to 3 m/s are studied. The results of this study are investigated for a single-axis tracking system at pitch angles 0°, 15°, 30°, and 45°, and for a two-axis tracking system for the angles of 45°–35°, 45°–25°, and 45°–15°, respectively. The results indicate that factors such as the change in the heat transfer coefficient, collector pitch angles, and amount of flow deviation between the upper and lower dome of the collector resulting in a distinction between the absorption of maximum radiation fluxes or the maximum heat transfer (heat loss) rate. Moreover, the higher the pitch angle, the higher the amount of received sunlight, but on the other hand, it causes the wind to affect all the collector surfaces (more heat loss). The drag force applied to the two-axis collector is lower than the one-axis collector. Therefore, using a two-axis system not only does not increase the structure size but also can decrease it, too.

2021-03

Journal of Molecular Liquids (Issue : 1) (Volume : 333)

This laboratory study investigates the effect of temperature and volume fraction of nanoparticles on the dynamic viscosity () of MWCNT - WO3 / water - Ethylene glycol (80:20) nanofluid. The nanofluids are synthesized using a two-step method by dispersion of nanoparticles in the base fluid. Nanofluid is synthesized in the volume fraction of nanoparticles of 0.1–0.6%. After ensuring the stability of the nanofluid, is measured at a temperature range of T = 25 °C–50 °C. The results show that as the increases at a constant temperature, the increases. On the other hand, as the temperature increases at a constant , of the fluid decreases. Finally, a mathematical model is proposed as a function of temperature and for estimation of the. The comparison of the results of the proposed relationship and the experimental results reveal the desired accuracy of the proposed model for this nanofluid.

2021-02

ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (Issue : 1) (Volume : 2021)

In the present numerical simulation, laminar single-phase and two-phase nanofluid flows are investigated inside a rectangular microchannel with the vortex generators. Rhombic vortex generators with different attack angles are used for a better mixture of fluid. Water/MgO nanofluid is used as the working fluid in the volume fractions of nanoparticles φ = 0-4% in Reynolds numbers of Re = 1-300 at the two-dimensional space. The presence of vortex generators with attack angles of λ = 0-45o, and simultaneous investigation of heat transfer and flow hydrodynamic parameters distinguish this research from other similar studies. Obtained results revealed that using nanofluid with higher volume fractions, slip boundary condition on the hot wall, and using vortex generator with higher λ lead to significant enhancement of heat transfer. Also, the value of pressure drop augmentation is caused by the increase of φ and λ is significant at higher Reynolds numbers. Unlike the increase of φ, by increasing Reynolds number, the effect of slip boundary condition becomes considerable on the reduction of entropy generation. The behavior of entropy generation graphs with slip velocity boundary condition on the wall is different from the no-slip boundary condition at Re = 300. The behavior of average entropy generation is different in the various φ, Reynolds numbers, and λ in the no-slip boundary condition for single-phase and two-phase models. Also, the two-phase model estimates flow behavior with less irreversibility.

2021-02

Advances in Difference Equations (Issue : 1) (Volume : 141)

The Hirota bilinear method is employed for searching the localized waves, lump–solitons, and solutions between lumps and rogue waves for the fractional generalized Calogero–Bogoyavlensky–Schiff–Bogoyavlensky–Konopelchenko (CBS-BK) equation. We probe three cases including lump (combination of two positive functions as polynomial), lump–kink (combination of two positive functions as polynomial and exponential function) called the interaction between a lump and one line soliton, and lump–soliton (combination of two positive functions as polynomial and hyperbolic cos function) called the interaction between a lump and two-line solitons. At the critical point, the second-order derivative and the Hessian matrix for only one point will be investigated and the lump solution has one maximum value. The moving path of the lump solution and also the moving velocity and the maximum amplitude will be obtained. The graphs for various fractional orders α are plotted to obtain 3D plot, contour plot, density plot, and 2D plot. The physical phenomena of this obtained lump and its interaction soliton solutions are analyzed and presented in figures by selecting the suitable values. That will be extensively used to report many attractive physical phenomena in the fields of fluid dynamics, classical mechanics, physics, and so on.

2021-01

Powder Technology (Issue : 3) (Volume : 380)

Heat sinks are always in the center of electronic cooling researchers' attention. Microchannels are utilized in electronic cooling devices owing to their increased surface and better thermal performance than that of normal heat sinks. In this numerical investigation, the first and second laws of thermodynamics impact of twisted porous ribs on the microchannel are studied. The effects of the Reynolds number, the Hartman number, and the volume fraction of nanoparticles are investigated. The range of the dimensionless number for the Hartmann number and the Reynolds number is 0 to 20 and 250 to 1000, respectively. All types of microchannel in this study consist of clear microchannels in two groups; group one (No. 1, 2 and 3) and group two (No. 4, 5, and 6). The obtained results show that at the end of each porous rib, the reported parameters depict a decrease. Twisted porous ribs cause a significant decrease in the expanding thermal boundary layer. Also, the microchannel with triple-layer porous ribs (No. 3) exhibits considerable performance in the entropy generation. Finally, since group one has a double pitch, it has the better thermal performance and increasing the Hartmann number is one of the reasons for the increasing velocity gradient near the microchannel wall and friction factor.

2021-01

ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (Issue : 1) (Volume : 59)

Nowadays, humans are suffering from chronic cardiovascular diseases, including Congenital Heart Defect (CHD). These diseases have far‐reaching consequences, such as disruption of the daily life of humans by reducing their ability to perform daily routines. This problem is due to impaired cardiac pumping capability. The present numerical simulation studied the effects of CHDs on pressure drop and AWSS. Numerical calculation of non‐Newtonian blood flow parameters, including power‐law indices and the Reynolds number, were also investigated. To construct a 3D model of CHDs, an OSS program using DICOM and MRI was used. Besides, the vessel wall was assumed as solid. The non‐Newtonian blood flow was assumed as a laminar flow with the slip boundary conditions at the vessel wall. AWSS, pressure drop, and dimensionless heat transfer coefficient are directly correlated with power‐law indices, Reynolds number, and constant heat flux boundary conditions of the body. CHDs increased velocity, pressure drop, and AWSS in all steps of the simulation process.

2021-01

ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (Issue : 1) (Volume : 59)

In this study, a numerical investigation of fluid flow and heat transfer of Al2O3‐water nanofluids in a pillow plate heat exchanger with a two‐phase model is investigated. The flow regime studied in this study is in the laminar flow regime such that the Reynolds numbers are 250, 500, 750, and 1000 and the volume fraction of the nanoparticles remained so that the fluid stayed in Newtonian. The volume fraction of nanoparticles is 𝜙= 0, 1, 2, and 3 %. In this study, the effect of the shape of the welding points used in the pillow plate has also been investigated in such a way that three modes of circular welding point, large‐diameter elliptic welding point along with the flow and large‐diameter elliptic welding point perpendicular to the stream have been investigated. Numerical simulation results show that using nanofluid and increasing Reynolds number improves heat transfer, as well as circular welding point, shows the best heat transfer rate. The shape of the welding points has a direct relationship with the pressure drop and heat transfer, as well as the wake created behind the welding points, which have the highest wake and pressure drop respectively for the elliptic welding points perpendicular to the flow, circular and elliptical parallel to the flow. On the other hand, the addition of nanoparticles increases the friction factor and, on the contrary, increases the Reynolds number, which reduces the friction factor. Finally, the highest Reynolds number, the highest volume fraction of nanoparticles, and the circular welding point state show the highest PEC. Early View Online Version of Record before inclusion in an issue e202000300 Related Information Metrics Details © 2021 Wiley‐VCH GmbH Keywords counterflow heat exchanger mixture model nanofluid pillow plate Publication History Version of Record online: 14 January 2021 Manuscript accepted: 05 January 2021 Manuscript revised: 19 November 2020 Manuscript received: 11 October 2020

2020-10

Scientific Reports (Issue : 4) (Volume : 10)

This study presents the frequency analysis of a size-dependent laminated polymer composite microtube using a nonlocal strain-stress gradient (NSG) model. By applying energy methods (known as Hamilton’s principle), the motion equations of the laminated micro tube composites are developed. The thermodynamic equations of the laminated microtube are based on first-order shear deformation theory (FSDT), and a generalized differential quadrature method (GDQM) is employed to find the model for the natural frequencies. The results show that by considering CF boundary conditions (BCs) and every even layers’ number in lower value of length scale parameter, the frequency of the structure drops by soaring this parameter. However, this matter is inverse in its higher value. Eventually, the ply angle’s influences, nonlocality as well as length scale element on the vibration of the laminated composite microstructure …

2020-10

Journal of Molecular Liquids (Issue : 1) (Volume : 321)

In this work, we describe the atomic effects of graphene nanosheets adding to the hydraulic fracturing process by molecular dynamics method. In our simulations, we study the nanosheets type effect on the fracturing process. For this purpose, we reported physical parameters such as temperature, potential energy, joint force, and the number of lost atoms from atomic substrates. In our approach, nanofluid, which used in hydraulic fracturing, is exactly simulated by various interatomic force fields. Our simulations show that adding graphene nanoparticles to the first fluid causes maximum atomic removal from simulated rock substrate. Numerically, after 2.5 ns, the departed atoms from rock substrate reach to 74 atoms. Furthermore, the atomic rate of graphene nanosheets is another important parameter in hydraulic fracturing. Our molecular dynamics results show that, by 5% atomic rate of graphene nanosheets to initial fluid, the departed atoms reach to the maximum rate (101 atoms). Finally, by adding graphene nanosheets with 4 nm length, the top quality of particles departed from the rock substrate.

2020-09

Heat Transfer Research (Issue : 15) (Volume : 51)

In this paper, an artifi cial neural network (ANN) has been studied for the viscosity of MWCNTs–ZnO/water–ethylene glycol (80:20 vol.%) non-Newtonian nanofl uid. To evaluate the rheological behavior of the nanocoolants, for each solid volume fraction and temperature, all experiments were repeated at diff erent shear rates. Aft er generating the experimental data, an ANN method is applied. The ANN is selected based on the diff erent generating architectures (neuron numbers). The algorithm for choosing the best ANN is presented. Also, using the correlation method, the viscosity of nanofl uid is predicted. Finally, ANN and correlation results are compared with the obtained data from the correlation method. It was found that the ANN had a bett er ability in predicting the viscosity of nanofl uid compared with the correlation method because the (MSE) of ANN was 0.0885, and the MSE of the correlation method was 0.9531. However, both approaches are useful, but ANN had a bett er ability to model the viscosity of nanofl uid based on the input values.

2020-09

Journal of Cleaner Production (Issue : 1) (Volume : 281)

The pollution of fossil fuels uses and low efficiency performance of energy systems are the main issues which threaten the environment and cause extra cost. Many solutions are presented and the one which is performed in this study is using energy hub which is composed of several parts. Sub energy hub and combined cooling, heating and power combining with the renewable energies such as wind turbine and photovoltaic are the component parts of this novel energy hub. The optimum flow of energy plus using energy storage devices brings coordination and reliability to the system. The model proposed is multi-objective and the goal is to investigate the effects of accomplishment real-time based demand response program in reducing operation cost and CO2 emission. The mathematical methods like compromise programming and fuzzy approach are implemented to gain the Pareto solutions and obtain trade-off between economic and environmental performances. Two cases which are investigated in this paper are without and with demand response program. The linear model with mixed-integer programming is implemented in general algebraic modeling system to solve the proposed model. The comparison results illustrate that the operation cost and CO2 emission is decreased 4.05% and 1.52% respectively due to demand response program.

2020-08

Journal of Molecular Liquids (Issue : 24) (Volume : 321)

In this computational work, we focus on spherical barrier effects on the thermal behaviour of Ar/Cu nanofluid with molecular dynamics simulation. LAMMPS software is implemented in our study with Universal Force Field and Embedded Atom Model force field for various atomic structures in the simulation box. The thermal behaviour study of Ar/Cu nanofluid is done with physical parameters calculations such as atomic temperature, total energy, number of nanofluid atoms at gas phase, radial distribution function, and thermal conductivity of Ar/Cu nanofluid. By atomic barrier adding to our simulated plates, the atomic phase transition occurs in fewer time steps. Numerically, phase transition in the simulated nanofluid occurs in 610,000-time steps by Pt spherical barriers simulation (with 15 Å radius). By increasing the atomic barrier size, the number of nanofluid atoms in which phase transition occur in them is increased. From these simulations results, we conclude that, heat flux in Ar/Cu nanofluid increases but thermal conductivity of the foremost constant. Numerically, the thermal conductivity of Ar/Cu nanofluid reaches to 0.016 W/m.K by atomic barrier radius increasing to 15 Å.

2020-07

Journal of Materials Research and Technology (Issue : 4) (Volume : 9)

In the current study, an experimental study was carried out on the rheological properties of hybrid non-Newtonian nanofluid (MWCNTs–ZnO/Water–Ethylene glycol (80:20 vol.%)) to develop a new model. The viscosities of nanofluid were evaluated in the temperature range of 25–50 °C with volume fractions of φ = 0.075%, 0.15%, 0.3%, 0.6%, 0.9%, and 1.2%. We find that the effect of changes is more obvious when the φ is increased. So the property of non-Newtonian nanofluid is more likely to appear. In addition to a temperature of 25 °C, the viscosity increase from a φ = 0% to 1.2% is higher than 90%, which is very significant. Also, in the maximum φ, at T = 50 °C, 40 °C and 30 °C, the viscosity reduction is 21%, 17%, and 8%, respectively, relative to the reference temperature (25 °C). The above results can be of great help to engineers in designing thermal systems to increase heat transfer and considering pumping …

2020-07

Mathematical Methods in the Applied Sciences (Issue : 12) (Volume : 22)

The present article deals with M‐soliton solution and N‐soliton solution of the (2 + 1)‐dimensional asymmetrical Nizhnik–Novikov–Veselov equation by virtue of Hirota bilinear operator method. The obtained solutions for solving the current equation represent some localized waves including soliton, breather, lump, and their interactions, which have been investigated by the approach of the long‐wave limit. Mainly, by choosing the specific parameter constraints in the M‐soliton and N‐soliton solutions, all cases of the one breather or one lump can be captured from the two, three, four, and five solitons. In addition, the performances of the mentioned technique, namely, the Hirota bilinear technique, are substantially powerful and absolutely reliable to search for new explicit solutions of nonlinear models. Meanwhile, the obtained solutions are extended with numerical simulation to analyze graphically, which results in …

2020-07

Renewable Energy (Issue : 3) (Volume : 161)

The financial risks imposed from the uncertain parameters is a considerable issue in the optimization problem of renewable-based energy systems. Due to the various risks in renewable-based energy systems, a practical and simple risk measurement approach can be efficient in the risk-based strategy selection process. In this paper, the downside risk constraints (DRC) approach as a novel risk measurement approach is proposed to manage the imposed risks from the uncertain parameters over the stochastic problems. Therefore, various uncertainties, including solar irradiation, temperature, wind speed, electricity demand, and electricity market price uncertainties, are modeled using the DRC approach along with the stochastic programming. In addition, the compressed air energy storage (CAES) and demand response program (DRP) is implemented to manage the imposed risks. By using the proposed risk …

2020-06

Journal of Materials Research and Technology (Issue : 4) (Volume : 9)

Reliable energy supply is a significant challenge for the power system operators. The increase of emerging resources, as well as multi-carrier consumers in energy systems, lead to the integration of multi-carrier energy systems. The energy hub (EH) is one of the central infrastructures which smooths the combination and interdependency of various energy carriers to increase the efficiency and reliability. A novel technology, such as power-to-gas (P2G) storage, is a great option for achieving a renewable resources-based integrated energy system with high efficiency. The P2G storage is regarded as a viable energy storage approach to cover ever-increasing renewable energy resources variability in power system operations. The contribution of this paper is to present an optimal stochastic scheduling problem of EH integrated with P2G storage, combined heat and power (CHP) unit, wind power, boiler, electrical storage, and thermal storage to meet electrical, heat, and gas demands considering demand response program (DRP). The load shifting based DRP is applied on the electrical loads to reduce the operation cost of the EH. Also, the P2G storage system is used as a new resource that makes a connection between electrical and natural gas networks by converting the power to hydrogen and after that to natural gas through two processes including electrolysis and mechanization, respectively. A scenario-based stochastic approach is applied to handle the uncertainties related to the electrical loads, wind power, and electricity price. The objective of the proposed problem is to minimize the total operation cost of EH, which is modeled as a mixed-integer linear programming (MILP) problem model. The numerical results are implemented for different cases which demonstrate the effectiveness of the integration of the P2G based multi-carrier energy storage and DRPs on the operation cost of EH. The achieved results confirm the proposed approach by demonstrating the considerable reduction in operating cost of the EHS by approximately 7%.

2020-06

Journal of Molecular Liquids (Issue : 2) (Volume : 12)

This work presents a study on the effects of roughness with a cone shape on the flow behavior of Argon fluid within a microchannel under phase change condition. The effective parameter on the results and discussion of this paper is propulsion force, which is exerted on the fluid at the entrance region of channels with roughened and smooth surfaces in order of 0.002, 0.01 & 0.02 eV/Å. Roughness elements with cone geometry performed their role in favor of augmentation of heat transfer from channel walls to fluid flow due to the enhancement of effective contact surface between microchannel and fluid. Therefore, it helps to the distribution of particles from lateral bins to central bins of microchannel due to the acceleration of the boiling process. But, increasing external force up to 0.02 eV/Å brings a noticeable instability in density profile at time step 1,000,000. Also, under worse cases of this study, the cone shape of …

2020-06

European Journal of Mechanics-B/Fluids (Issue : 6) (Volume : 14)

In this paper, we used the Hirota bilinear method for investigating the third-order evolution equation to determine the soliton-type solutions. We probe five cases including lump, lump-kink called the interaction between a lump and one line soliton, lump-soliton called the interaction between a lump and two-line solitons, kinky breather-soliton and finally the stripe soliton function only with exponential solution function. The theorem along with the proof for the considered problem is given. Moreover, to more investigating the moving velocity, the maximum amplitude and also moving pass function are obtained. The existence criteria of these solitons in the unidirectional propagation of long waves over shallow water are also demonstrated. Different arbitrary parameters received in the solutions help us to discuss the physical interpretation of solutions that can be linked with a large variety of physical phenomena.

2020-06

Communications in Theoretical Physics (Issue : 7) (Volume : 72)

The multiple lump solutions method is employed for the purpose of obtaining multiple soliton solutions for the generalized Bogoyavlensky–Konopelchenko (BK) equation. The solutions obtained contain first-order, second-order, and third-order wave solutions. At the critical point, the second-order derivative and Hessian matrix for only one point is investigated, and the lump solution has one maximum value. He's semi-inverse variational principle (SIVP) is also used for the generalized BK equation. Three major cases are studied, based on two different ansatzes using the SIVP. The physical phenomena of the multiple soliton solutions thus obtained are then analyzed and demonstrated in the figures below, using a selection of suitable parameter values. This method should prove extremely useful for further studies of attractive physical phenomena in the fields of heat transfer, fluid dynamics, etc.

2020-06

Journal of Cleaner Production (Issue : 8) (Volume : 34)

Among different renewable energies, the sun as an endless source of energy has been the focus of many researchers worldwide. The use of solar radiation energy in conventional power generation systems can play an important role in reducing fuel consumption and environmental pollution. The importance of this energy has been increased when we need to supply the load demand, especially in desert-like places. The main objective of this research is to propose a new optimal hybrid solar/diesel/battery system to cover the demand load of a rural part in the Gobi Desert in China. The main objectives for optimization are the loss of load probability, CO2 emissions value, and the annualized cost of the system. Here, the ε-constraint method is adopted to simplify the multi-objective problem into a single objective problem. The optimization of the problem is performed by a developed version of the elephant herd …

2020-05

Medical Hypotheses (Issue : 2) (Volume : 11)

In this work, the Sisko model is involved for blood flow simulation in the arteries with triangular shapes of stenosis, which is different in severities of 20%, 30%, and 40%, respectively. Firstly, the effects of different severity of stenosis as much as 20%, 30%, and 40% are investigated in the velocity of blood while artery radius of 0.002m and Sisko parameters of n=0.639 and b=0.1735 are constant. Then, stenosis with the severity of 40% remains, and the radius of the artery is varied from 0.002m to 0.0035m to investigate the effects of artery radius on the blood velocity. Finally, different types of blood fluids are employed by manipulation of Sisko parameters, and influences of blood fluid behaviors are investigated in velocity profiles. It is reported that influences of increasing severity of stenosis and reducing the radius of the artery cause blood velocity to be augmented due to the role of stenosis as an obstacle against blood …

2020-05

Advances in Difference Equations (Issue : 1) (Volume : 20)

In this paper, we use the Hirota bilinear method for investigating the third-order evolution equation to determining the soliton-type solutions. The M lump solutions along with different types of graphs including contour, density, and three- and two-dimensional plots have been made. Moreover, the interaction between 1-lump and two stripe solutions and the interaction between 2-lump and one stripe solutions with finding more general rational exact soliton wave solutions of the third-order evaluation equation are obtained. We give the theorem along with the proof for the considered problem. The existence criteria of these solitons in the unidirectional propagation of long waves over shallow water are also demonstrated. Various arbitrary constants obtained in the solutions help us to discuss the graphical behavior of solutions and also grants flexibility in formulating solutions that can be linked with a large variety of physical phenomena. We further show that the assigned method is general, efficient, straightforward, and powerful and can be exerted to establish exact solutions of diverse kinds of fractional equations originated in mathematical physics and engineering. We have depicted the figures of the evaluated solutions to interpret the physical phenomena.

2020-03

Scientific Reports (Issue : 1) (Volume : 10)

This paper presents the effects of barriers with cubic geometry on the boiling flow behavior of Argon flow with 10 million atoms flowing inside smooth and rough microchannels using molecular dynamic simulation (MDS) method. Effective parameters of this research are boundary temperature of 108 K on the walls of microchannels to prepare boiling condition and driving forces as much as 0.002, 0.01, and 0.02 eV/Å, which is enforced respectively on the fluid at the inlet of the microchannel. For ease of investigation in comparison to results by statistical method, the cubic shape of roughness barriers is simulated on the surfaces of a smooth microchannel with the same dimensions. Results showed that the presence of cubic roughness elements increases oscillations in density profiles due to their influences in arrangements of argon atoms and their consequences in the diminishing role of the boiling process to move …

2020-03

Physica Scripta (Issue : 6) (Volume : 95)

This paper aims at investigating periodic wave solutions for the (2+ 1)-dimensional KP-BBM equation, from its bilinear form, obtained using the Hirota operator. Two major cases were studied from two different ansatzes. The 3D, 2D and density representation illustrating some cases of solutions obtained have been represented from a selection of the appropriate parameters. The modulation instability is employed to discuss the stability of got solutions. That will be extensively used to report many attractive physical phenomena in the fields of acoustics, heat transfer, fluid dynamics, classical mechanics and so on.

2020-03

The European Physical Journal Plus (Issue : 3) (Volume : 135)

In this research paper, we try to illustrate the structure of the novel exact soliton wave solutions of nematicons in liquid crystals with four law nonlinearity forms including the Kerr, power, parabolic and dual-power by utilizing the-expansion method. The aim of this research is not just to find the dark, bright, combined dark-bright, singular types, traveling and solitary solutions of nematicons in liquid crystals by investigating the aforementioned method, showing the differences between the obtained solutions and other solutions obtained by using different methods. Moreover, constraints guarantee the existence of the obtained solutions. Eventually, we believe that the enforced method is more powerful and efficient than other methods and the obtained solutions in this paper can help us to understand soliton molecules in liquid crystals. That will be extensively used to describe many interesting physical phenomena …

2020-02

The European Physical Journal Plus (Issue : 2) (Volume : 135)

In this paper, we have earned the M-lump solutions, the interaction within stripe solitons and lumps which are more considered mentioning that lumps will be drowned or swallowed by the stripe solitons. By utilizing the Hirota bilinear method and via the symbolic calculations, solve the ()-dimensional Kadomtsev–Petviashvili–Benjamin–Bona–Mahony (KP-BBM) equation. We obtain some multiple collisions of lumps. Next, the interactive solutions between M-lumps and N-stripe solitons have very enhanced the existing literature on the KP-BBM equation. Through the three-dimensional plots, contour, and two-dimensional plots by utilizing Maple software, the physical properties of these waves are described very well. That will be extensively used to describe many interesting physical phenomena in the areas of gas, plasma, optics, acoustics, heat transfer, fluid dynamics, classical mechanics, and so on. These new …

2020-02

Mechanics (Issue : 1) (Volume : 26)

The numerical simulation of the flow of fluid through one or a set of objects that causes the flow to separate from the surface of them has been the subject of interest by researchers over the past few decades. One of the most important types of these objects is those with a square cross section which have important and diverse applications in different industries. One of the practical applications of these types of streams is flow around chimneys, high-rise buildings, naval structures, suspended bridges, airplane wings, ship propellers and ducts. In this research, the immersed interface method is used which is a non-conforming method to the boundary. Eulerian mesh for fluid field, and Lagrangian mesh for solid field is used. The connection of these two networks is established by the Dirac Delta function. Considering the cylinder as a rigid immersion boundary within the flow. First, the flow around a square cylinder was simulated and we surveyed different flow patterns. The changes in the number of Strouhal and the Drag coefficient were investigated in different Reynolds. The flow around the two cylinders was simulated. It was observed that with the increase of Reynolds number and the gap between cylinders, the vortex shedding (Strouhal number) would increase.

2019-12

Iranian Journal of Science and Technology, Transactions of Mechanical Engineering (Issue : 4) (Volume : 43)

In the present study, the dynamics of a red blood cell (RBC) in a simple microchannel and in a microchannel with obstacle is simulated using combined lattice Boltzmann-immersed boundary method. The fluid flow field is solved for using LBM and the interaction between the fluid and the RBC is simulated using the IBM. The RBC is considered as a deformable boundary immersed in the fluid flow. When the RBC is stiffer, the flow passage is further blocked due to the lack of flexibility of the RBC causing the flow velocity to decrease and greater drag force (resistance force against the motion of cell) from the fluid to be exerted on it. As a result, the pressure around the RBC increases and becomes even higher than the inlet pressure of microchannel. This increased pressure is thought to be the reason of many serious diseases including cardiovascular diseases. If the number of RBCs used in the simulation …

2019-12

Nexo Revista Científica (Issue : 2) (Volume : 32)

La luz del día es una de las fuentes de luz más importantes que podría iluminar los espacios interiores al pasar a través de ventanas y colectores de luz. La acumulación de polvo y aerosoles en los cristales de las ventanas reduce la cantidad de luz que pasa a través de ellos. El objetivo principal de esta investigación es determinar el impacto de la deposición de partículas en el aire sobre la cantidad de luz pasada. En este experimento, se obtuvieron las partículas más prevalentes, como el polvo, el carbono y una mezcla de ambos examinados con vidrios comerciales comunes de 3 mm en cristales de vidrios simples y dobles y se obtuvieron varias observaciones interesantes. El resultado de este experimento ayudará a los propietarios de edificios a ajustar un programa de limpieza de ventanas para reducir el consumo y los gastos de electricidad de iluminación.

2019-12

Advances in Science and Technology. Research Journal (Issue : 4) (Volume : 13)

Immersed interface method is a non-matching boundary approach that has been taken into consideration in recent years. In this method, there is no need to coincide between the fluid and the solid grids. Eulerian grid is used for fluid domain and Lagrangian grid is used for solid domain. Using the Dirac Delta function, the connection between these two grids is established. Separation of the flow from the cylinder surface causes a high pressure drop in some parts of the cylinder, resulting in a dramatic increase in drag force. Drag force reduction is very important in some engineering issues, and several methods have been proposed to achieve this goal. In this study, the flow around a rigid cylinder is simulated. The goal is to reduce the drag force on the cylinder through one and two horizontal plates. The results are in good agreement with prior numerical results.

2019-11

Ceramics International (Issue : 16) (Volume : 45)

In this study, the microstructural and mechanical properties of three different mullite matrix composites were investigated. Accordingly, Mullite-TiN-CNT, Mullite-TiN-TiB2-CNT and Mullite-TiN-TiB2-ZrB2-CNT composites with 10 wt % of each TiN, TiB2 and ZrB2 reinforcement particles as well as 1 wt % CNT were prepared by the spark plasma sintering (SPS) technique. The sintering processes were conducted at 1350 °C for 5 min with a mean heating rate of 60 °C/min. The relative densities of the composites achieved were higher than 97% of theoretical density. The results of mechanical properties of the fabricated composites showed that Mul-TiN-TiB2-ZrB2-CNT composites obtained the highest hardness and fracture toughness values. XRD results confirmed the presence of mullite, TiN, TiB2 and ZrB2 phases without any additional reactions between reinforcement and matrix phases. Microstructural studies …

2019-11

Sustainable Cities and Society (Issue : 6) (Volume : 51)

As enlarging share of renewables brings up a promising future for clean power generation, nonetheless, it imposes new challenges into the secure operation of power systems such occurrence of distasteful congestion, discriminatory locational marginal pricing (LMP) and also increasing uncertainty and inflexibility. To address these issues, a novel chance constrained two-stage programming is developed, where in the first stage social welfare of system is maximised while in the second stage a stochastic security constrained unit commitment problem is executed along with compressed air energy storage (CAES) and demand response program (DRP) to minimize both operation costs and wind curtailment. Both DRP and CAES are cooperatively applied to maximize wind proliferation and social welfare, alleviate the congestion of network, smooth LMP at different nodes, and improve technical characterizations of …

2019-11

Materials Research Express (Issue : 12) (Volume : 6)

This study aims to investigate the effect of time and temperature of complete and partial solutionizing heat treatment on the coarsening of γ'precipitates in rejuvenation treatment of the used gas turbine blade IN738LC worked for 60000 h. During long-term heating (simulated under the service conditions). After the sample preparation and rejuvenation treatment, long-term heating was carried out at 900 C and 1000 C for 500 to 2500 h. The SEM results showed that after rejuvenation with increasing temperature and time, γ'precipitates coarse in all the samples and the coarse γ'precipitates appear with spherical morphology. It was observed that the amount of secondary γ'precipitates decreases with the increase in temperature. When the solution treatment temperature drops, the amount of coarsened γ'precipitates has increased, which shows that the temperature rise results in a lower coarsening rate and smaller …

2019-11

Advances in Science and Technology Research Journal (Issue : 3) (Volume : 13)

In this study, melting of a phase changing material enriched with nanoparticles in a circular ring-rectangular enclosure was investigated and the results were analyzed. At the beginning of the melting process in the absence of a natural displacement, the mechanism of conduction heat transfer around the hot cylinder is the dominant mechanism. Over time, natural displacement gradually appears and deforms the melting boundary above the cylinder. Over time, when the thickness of the liquid phase grows, the thermal resistance increases, this can be verified by reviewing the Nusselt chart. So this phenomenon reduces the rate of melting and temperature changes. The results show that increasing the nanoparticle volume fraction due to increased conductivity and decreasing latent heat causes an increase in the melting rate and the amount of energy absorbed. From the study of various volume fractions, it can be concluded that the use of a higher volume fraction of 3% is more appropriate both in terms of energy and in terms of the melting rate. However, it should be taken into account that if the melting rate exceeds this value, it may cause agglomeration and deposition of nanoparticles and reducing system efficiency.

2019-10

Materials Research Express (Issue : 11) (Volume : 6)

In this paper, hot corrosion and oxidation behavior of Ti–6Al–4V alloys, which undergo different heat treatment, is investigated. For this purpose, four samples with different thermal histories were prepared by annealing, solutionizing, quenching in water and air and finally aged. The solutionizing temperature was 800 and 950 C. Also, the aging temperature was 1050 C. After the heat treatment process, the samples were exposed to a hot corrosion environment with a mixture of 60% V 2 O 5+ 40% Na 2 SO 4 as well as the oxidation process in the air. Microstructural and phase studies were performed by Field Emission Scanning Electron Microscopy (FESEM), and x-ray Diffraction (XRD), respectively, demonstrated that the samples that solution treated in 1050 C for 1 h then quenched in water and aged at 550 C for 4 h has the lowest hot corrosion and oxidation rate. Achieving maximum hot corrosion resistance without …

2019-10

Journal of Electronic Materials (Issue : 1) (Volume : 49)

Core–mantle–shell supramolecules composed of carbon nanotube (CNT)-graft-polyaniline (PANI), poly(3-hexylthiophene) (P3HT), and poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT) precursors were designed and utilized in PBDT-DTNT:phenyl-C61-butyric acid methyl ester (PC61BM) solar cells. Weight ratio of polymer:CNT-graft-PANI was 9:1 and the weight ratios were 1:1 in binary and 1:1:1 in ternary systems. Diameters of core(CNT)–mantle(PANI), core(CNT)–mantle(PANI)–shell(P3HT), and core(CNT)–mantle(PANI)–shell(PBDT-DTNT) nanostructures ranged in 75–90 nm, 145–160 nm, and 120–130 nm, respectively. Efficacies of 6.82% (13.92 mA/cm2, 0.71 V, 69%, 7.1 × 10−3 cm2/V s and 1.9 × 10−2 cm2/V s) and 7.60% (14.66 mA/cm2, 0.73 V, 71%, 9.0 × 10−3 cm2/V s and 3.4 × 10−2 cm2/V s) were acquired for photovoltaics based on the …

2019-09

Waves in Random and Complex Media (Issue : 5) (Volume : 53)

This article investigates the influences of nonuniform imperfection on the dynamic amplitude and resonance frequency of the nanoshell reinforced with graphene nanoplatelet (GNP). The novelty of the current study is to consider the effects of porosity, thermal loading and graphene platelet reinforced composites on the dynamic behavior of the nanostructure. Three-length scale parameters (l0 = 5 h, l1 = 3 h, l2 = 5 h) in the modified strain gradient theory (MSGT) show a better agreement with MD simulation in comparison with other theories. Finally, the effects of different factors on the dynamic amplitude and resonance frequency of the porous nanostructure are examined in detail.

2019-08

Mechanics (Issue : 4) (Volume : 25)

The interaction between incompressible fluids and elastic and rigid boundaries is seen in many medical, engineering and natural issues. The immersed interface method is used as a non-conforming meshes method to simulate such problems. In this method, the effect of the presence of a body immersed in a fluid is considered by adding a force term to the Navier-Stokes equations. An important advantage of this method is that there is no compulsion to adapt the fluid grids and the boundary grids. First, the flow around a circular cylinder was simulated. As the Reynolds number rises, the vortex dimensions become larger and, as a result, the separation angle of the flow increases. Also, with the Reynolds number increasing, the drag coefficient decreases and the Strouhal number increases and the flow separated from cylinder and two symmetrical vortices is generated behind the cylinder. Then, the behavior of an elastic boundary in shear flow was investigated. It was observed that by increasing bending modulus (increasing stiffness) of body the shape change of the boundary decreases. As well as the tank-treading motion is also observed that this type of movement has been confirmed in experiments. Also observed that the sick cell makes smaller defor-mation, while the normal cell is more deformed and easier passes the stenosis. This results in reduction of the flow rate in stenosis. This behavior is caused by a type of dis-ease called sickle cell anemia.

2019-08

Materials Research Express (Issue : 10) (Volume : 6)

In this study, Self-catalytic electroless coating process was applied in order to improve wear resistance and surface hardness of bronze. Through this process, the uniform coating of Ni–B with 7 μm thickness was formed. Microstructural study with the field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD) showed that cauliflower and completely amorphous structure with excellent adhesion was formed on the substrate. Formed Ni–B coating with a microhardness of 788 (HV 100) leads to a 40% increase in hardness compare to the substrate. In order to increase the surface hardness, coated samples were heat-treated at temperatures of 310, 410, and 510 C for 70 min. The hardness of samples increased to 1365 (HV 100) after heat treatment and from 410 C to above hardness decrease. The result of x-ray diffraction showed that at 310 C Ni–B coating completely was crystallized and Ni 2 B …

2019-06

International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) (Issue : 4) (Volume : 9)

TWO-DIMENSIONAL SIMULATION TO INVESTIGATE THE INTERACTION OF FLUID-STRUCTURE INSIDE A MICROCHANNEL WITH ELASTIC AND RIGID BOUNDARY

2018-02

Theoretical and Computational Fluid Dynamics (Issue : 1) (Volume : 32)

In this paper, the motion of high deformable (healthy) and low deformable (sick) red blood cells in a microvessel with and without stenosis is simulated using a combined lattice Boltzmann-immersed boundary method. The RBC is considered as neo-Hookean elastic membrane with bending resistance. The motion and deformation of the RBC under different values of the Reynolds number are evaluated. In addition, the variations of blood flow resistance and time-averaged pressure due to the motion and deformation of the RBC are assessed. It was found that a healthy RBC moves faster than a sick one. The apparent viscosity and blood flow resistance are greater for the case involving the sick RBC. Blood pressure at the presence of stenosis and low deformable RBC increases, which is thought of as the reason of many serious diseases including cardiovascular diseases. As the Re number increases, the …

2018-02

Applied Mathematical Modelling (Issue : 6) (Volume : 54)

In this research, the dynamics of elastic membrane(s) having different elastic modulus in a microchannel with stenosis is simulated numerically using a combined lattice Boltzmann-immersed boundary (LB-IB) method. The membranes are considered as elastic boundaries immersed in the fluid flow. In IBM, the immersed boundary is represented in Lagrangian coordinates, while the fluid flow field is discretized by a uniform and fixed Eulerian mesh. Interaction between the fluid and the membranes is modeled using an appropriate Dirac delta function. The results were found to be in good agreement with available numerical data. First, the motion and deformation of a single elastic membrane in a microchannel with stenosis is studied and the influences of shear elastic modulus and bending resistance on the membrane deformation are evaluated. It was found that by increasing the elastic modulus, the deformation and …

2018-01

Journal of Computational Applied Mechanics (Issue : 6) (Volume : 32)

In the present study, the combination of lattice Boltzmann and immersed boundary methods is used to simulate the motion and deformation of a flexible body. Deformation of the body is studied in microchannel with stenosis and the effect of the flexibility changes on its deformation is investigated. The obtained results in the present manuscript show that by increasing the elasticity modulus, the deformation of the body and its speed decrease. In this case, the flow pressure around the body increase. When the body is initially located outside the microchannel center, tank-treading motion occurs due to the difference in velocity of the shear layers. In addition, with a decrease in the size of microchannel stenosis, the body is less deformed and goes faster and reaches to the end of the microchannel in less time. The faster or slower movement of the biological membranes than the normal state causes the proper exchange of materials between the membrane wall and the surrounding flow and that disturbs its most important duty ie the exchange of materials with tissues. The analysis in this study shows that the results of the simulation are in good agreement with the available results and demonstrates the efficiency of the combination of lattice Boltzmann and immersed boundary methods to simulate the dynamic behavior of biological membranes, red blood cells and deformable particles inside the flow.

2017-08

journals.tabrizu.ac.ir (Issue : 6) (Volume : 21)

In the present study, the dynamics of a red blood cell (RBC) in a simple microchannel and in a microchannel with step stenosis is simulated using combined lattice Boltzmann-immersed boundary (LB-IB) method. The RBC is considered as a deformable boundary immersed in the fluid flow. The effects of plasma viscosity on the motion and deformation of the RBC was investigated. Then the motion of a circular RBC in a Poiseuille flow was analyzed. Since the RBC is put at the centerline of the channel and the flow in the channel is axisymmetric, the lift forces acting on the top and bottom part of the RBC are in equilibrium. When passing over a step stenosis in the channel the normal RBC was found to be more deformable and take higher speed as compared to the less deformable RBC. In addition, the normal RBC experienced tank-treading motion due to its low elastic and bending coefficients whereas for the less …

2016-10

Modares Mechanical Engineering (Issue : 8) (Volume : 16)

In this paper, motion of a flexible membrane and hydrodynamic interaction of multiple membranes in a microchannel are simulated by developing a computer code written in C. The membranes are considered as flexible boundaries immersed in the fluid. First a single biconcave shaped membrane with high rigidity is considered. Due to the rigidity of the membrane, it experiences tumbling motion and its vertical displacement becomes oscillatory. Then, the effects of initial position of a circular membrane on its deformation, vertical velocity and displacement are investigated. It was observed that as the initial location of the membrane approaches the channel’s central axis, its vertical displacement and velocity decreased, but its horizontal velocity component increased. Finally, the simultaneous motion of multiple membranes in a microchannel and their interaction with each other and with flow are evaluated. The …

2016-01

Journal of Computational Science (Issue : 6) (Volume : 12)

In this study, the motion, deformation and rotation of two elastic membranes in a viscous shear flow in a microchannel with and without a groove are simulated utilizing a combined LBM–IBM. The membranes are considered as immersed elastic boundaries in the fluid flow. The membranes are represented in Lagrangian coordinates, while the fluid flow field is discretized by a uniform and fixed Eulerian mesh. The interaction of the fluid and membranes is modeled using an appropriate form of the Dirac delta function. Two geometrically different channels, namely, a simple channel and a channel with a groove are considered. In the simple channel case, when the membranes are placed on the symmetry axis of the channel, they continue to move and deform without any lift force and rotation induced. However, when the membranes are located off the symmetry axis, the pressure difference produced in the flow around …

2016-01

Modares Mechanical Engineering (Issue : 10) (Volume : 15)

In the current study, the motion and deformation of an elastic membrane in a two-dimensional channel with and without a groove is simulated using a combined lattice Boltzmann-immersed boundary method. The lattice Boltzmann method is used to solve the fluid flow equations and the immersed boundary method is used to incorporate the fluid-membrane interaction. The elastic membrane is considered as a flexible boundary immersed in the flow domain. In the immersed boundary method, the membrane is represented in the Lagrangian coordinates while the fluid domain is discretized on a uniform fixed Eulerian grid. The interaction between the fluid and the membrane is modeled using Dirac delta function. The effects of no-slip boundary condition are enforced by addition of a forcing term to the lattice Boltzmann equation. Depending on the flow rate, the initial location and stiffness of the elastic membrane, the …