mohammad sefid

The target of this research is to investigate the amount of entropy production during natural convection inside a 2D chamber containing a non-Newtonian nanofluid using the lattice Boltzmann method. The chamber is exposed to uniform heat absorption/production and uniform and non-uniform magnetic field at different angles. The feature of the present work is to evaluate the effect of thermal radiation and the shape of the cavity cold wall in three shapes: smooth, curved and diagonal on the flow characteristics. Application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research. Acceptable agreement of the obtained results with previous related studies confirmed the validity of the presented results. Based on the results, the presence of radiation parameter leads to the improvement of heat transfer, which is more evident due to the increase of fluid power-law index. In addition to reducing the Nusselt value for enhancing the fluid power-law index, the effectiveness of the presence of the magnetic field in reducing the entropy and heat transfer rate enhances as the fluid power-law index decreases. It is feasible to attain the flow strength and the Nusselt value up to 40% and 61% more, respectively, by applying a vertical and non-uniform magnetic field. Although for heat production mode, there will be the lowest value of thermal performance index and the Nusselt value, the greatest influence of the magnetic field is observed in the heat production mode. By designing the wall in a smooth shape, in addition to increase the thermal performance coefficient, it is possible to decline the Bejan value.

Paraffin waxes are widely used as commercial organic heat storage phase changes (PCM) for many applications due to their suitable properties. Significant heat from fusion, nonpoisonous and stable properties, no phase separation, and the phase process result in a small volume change. Meanwhile, they are subject to low thermal conductivity. The thermal conductivity of PCMs can be increased by different techniques such as the use of dispersion of particles or nanomaterials with high conductivity in PCM and the use of metal foams. The use of nanoparticles has such disadvantages as high cost and particle deposition after various cycles. Hence, in this study, some experiments were carried out to investigate the effect of porous media like copper foam and iron wool as the filler instead of nanomaterials on improving the heat conductivity of PCM. The results show that the porous foam increases the heat transfer and during the charging operation, the temperature of the porous plate wall increases continuously at the same rate as the paraffin. At 2400 s, the temperature of pure PCM, iron wool, and copper foam reaches 67.3, 72.5, and 73.27℃, respectively. The optimal mode is the one in which the copper absorber plate is connected to the copper foam, thus reducing the charging time by 600 s compared to pure PCM and saving 75% of energy. Connecting the copper absorber plate to the iron wool has a good thermal performance and stores 70.83% of energy. Thus, iron wool has an acceptable performance and is suitable for storage systems.

In this research, a novel trigeneration system driven by biomass-solar energies has been investigated from energy exergy, economic and environmental viewpoints. The solar energy is used to produce hydrogen (by a PEM electrolyzer powered by thermal photovoltaic panels). To meet the intermittent nature of solar energy, it is used for hydrogen production. The hydrogen is used as fuel in the combustion chamber. The proposed gas turbine cycle consists of two high and low-pressure turbines and two compressors with an intercooler. A combined organic Rankine-vapor compression refrigeration cycle that uses the recovered heat from the gas turbine is used to produce refrigeration and air cooling in the interstage compressor. The obtained results provide that the combination of solar-based hydrogen production and biomass-based gas turbine leads to an increase in power production capacity. The proposed combined system provides an energy and exergy efficiency of 21% and 17% and the emission of 0.00884 kg/s of CO2. The highest capital cost rate among the components is attributed to the PEM electrolyzer, amounting to 15.44 $/hr, and the total cost of the products has reached 0.5627 $/MJ. Using an intercooler, the energy and exergy efficiencies of the system have increased by 6% and 4%, respectively.

Today, solar desalination is one of the promising solutions for the problem of drinking water shortage, mainly in remote and low-population areas. In the present research, a solar still with passive external condensers was designed. To store the thermal energy in the basin of this solar still, paraffin wax was used in copper tubes as phase change materials. To compare and investigate the performance of the proposed solar still, a conventional solar still with the same specifications and dimensions was built and tested. Both solar stills were investigated on the days of 28 April, 5 and 9 May. The results of the experiments showed that the performance of the proposed solar still was better than the conventional solar still; the highest produced fresh water was 3.55 and 3.04 lit/m2 day, respectively, for the proposed and conventional solar stills, which showed a 17% increase in productivity per day. It is clear from past research that the condenser increases the temperature difference between the glass covers and the saltwater of the basin, but causes the temperature of the saltwater basin to decrease. However, in this research, in addition to the increase in the temperature difference between the glass cover and salt water, the amount of salt water also increased, and this trend of increasing temperature was observed until the end of the day in all three experiments, which shows the effective performance of paraffin wax in the basin of solar still.

The cooling process of parts in limited spaces is of great interest to researchers due to its many applications in industries such as electronics. Therefore, achieving the best performance of such systems has always been one of the challenges facing researchers. Due to this necessity, in the present simulation via the lattice Boltzmann method (LBM), the cooling of two hot semi-cylinders via magnetohydrodynamics (MHD) free convection has been interrogated. The novelty of the available study compared to antecedent studies is the effect of a magnetic field (MF) in different types and heat absorption for cooling two hot objects embedded within a triangular enclosure comprising non-Newtonian ferrofluid, which has not been studied so far. The accuracy of the obtained results was guaranteed via the validation of the written code in comparison with other studies qualitatively and quantitatively. Based on the results, To have a larger the Nusselt (Nu) value, at the highest Rayleigh (Ra) value, it is sufficient to decline the fluid power-law (PL) index, heat absorption index and the Hartmann (Ha) value. The reduction of in the mean Nu value due to rise of the Ha value for the shear thinning fluid is about 59%, while it is about 38% and 21% for the Newtonian and the shear thickening fluids, respectively. The existence of heat absorption, in addition to reducing the Nu value by about 75% in highest value, for the shear thinning fluid, results in a decrease in the value of thermal performance index (ITP), which is very insignificant for the shear thickening fluid at Ha=60. The predominance of conduction over convection is the result of enhancing the PL index, which diminishes the effect of type and power of MF. For Ra=104, due to low convection effects, changing the type of MF is ineffective, while for Ra=106, this effect is highest. By changing the angle of inclination of the chamber and changing the arrangement of hot objects on the walls of the cavity, by changing the flow patterns, the thermal characteristics of the system can be strongly affected. In all cases, the trend of the ITP changes is in accordance with the trend of the mean Nu changes, which exhibits that HT has the largest share to production entropy (PE).

The purpose of this analysis using lattice Boltzmann method (LBM) is to investigate the matter with which strategies can be used to control the amount of heat transfer and entropy formation. For this goal, the mixed convection heat transfer of non-Newtonian nanofluid under the impact of the magnetic field inside the square chamber containing the conductor wall has been analyzed. The results depicted that the flow characteristics and heat transfer are strongly affected by changing the position in these places. If the magnetic field is applied at the same location as the speed application position, the effect of increasing the Hartmann number in reducing the average Nusselt number becomes more evident. In order to have the highest value of Nusselt number, CASE3 should be considered, however, the greatest impact of magnetic field on fluid flow was observed for CASE2. By increasing the distance between the conductive wall and the moving wall, the average Nusselt number increases up to 1.5 times. By decreasing the thermal conductivity ratio from 10 to 0.5, the average Nusselt number decreases to about 55%. The entropy value has a direct/inverse relationship with the Richardson number/power-law index.

The usage of multi-generation systems is quickly developing in recent years. The present study analyzes the energy, exergy, economic and environmental (4E) of a novel Rankine organic cycle to produce power, hydrogen and fresh water with a combined energy source of geothermal and heat recovery. Also, the cycle performance in both modes with and without geothermal energy is compared. Calculations show that the highest percent of exergy destruction is equal to 35% and is related to the PEM Also, the lowest amount of exergoeconomic factor is calculated for the PEM is equal to 8.39 The amount of hydrogen and desalinated water produced is 1.64 lit/s and 4.36 kg/s, respectively. With increasing the temperature of the geothermal source from 125 to 155°C, the amount of hydrogen and desalinated water produced are 29 and 17 percentage increases, respectively. If geothermal energy is not used and all energy is supplied by heat recovery, the amount of carbon dioxide emitted will increase to 69%.

Numerical simulation of multiphase problems with complex interface as well as high density ratios is one of the numerical challenges associated with particle scattering and divergence. Fewer problems have been performed with density-based smooth particle hydrodynamics (WCSPH) to solve complex joint surface currents, and most simulations have been performed using Incompressible Smooth Particle Hydrodynamics (ISPH). Solution of high density flows by the smooth particle hydrodynamics is associated with particle dispersion and divergence. Various methods have been used to eliminate the scattering of particles, such as a repulsive force at the interface or the corrected density re-value, but there is a problem of particle disintegration at the interface at higher times. In the present simulation, to simulate multiphase flows with complex surfaces and high density ratios, a new density-based smooth particle hydrodynamics approach has been utilized. To prevent the scattering of particles, especially at the interface at the end times, a simple method with the removal of incompatible particles is used. In the present study, the particle displacement optimization scheme for regularization at the interface of the phase is created by precisely implementing a two-stage change algorithm, so as to maintain the regular particle distribution continuously and conservatively. To examine the accuracy of the present simulation method, it is firstly compared with two-phase Poiseuille flow with three fluids having different values of viscosity, Reynolds-Taylor instability and single bubble rising in a fully filled container., Then it is compared with analytical and numerical solutions. The accuracy and consistency of the current simulation is higher or equal to other simulations.

In the present work, heat transfer and entropy generation due to the natural convection of Newtonian and non-Newtonian fluids in two types of shear thinning and shear thickening inside a right-triangular cavity under the effect of uniform and non-uniform magnetic field by multiple relaxation time lattice Boltzmann methods have been investigated. The aspect ratio of the cavity is variable and the magnetic field is applied from left to right and perpendicular to the gravity of the cavity. The present work is validated with previous references and results presented in the form of tables, diagrams and streamlines, isothermal lines, and entropy lines. The simulation is done by writing the computer code in the Fortran language. The effect of Rayleigh number, aspect ratio, power-law index of fluid, Hartmann number and angle, and type of magnetic field applied on fluid flow and heat transfer characteristics has been evaluated. The results show that in all cases, increasing the Hartmann number and fluid power-law index leads to a decrease in the strength of flow, heat transfer rate, and entropy generated and the percentage of this effect varies depending on the number of other variables. By applying a magnetic field non-uniformly, the flow strength and heat transfer rate can be increased to about 45% and 20%, respectively. At higher Hartmann numbers, the effect of changing the type of magnetic field applied is more pronounced. The angle of the magnetic field applied is a determinant parameter on the amount of heat transfer so that the average Nusselt number in the horizontal mode is on average 15% less than in the vertical mode. Increasing of power-law index dramatically reduces the magnetic field effect so that it is ineffective for the shear thickening fluid, the type of magnetic field applied. By increasing the Rayleigh number and the aspect ratio of the cavity, the flow strength and the rate of heat transfer increase and the effect of the magnetic field becomes more pronounced. This study can be useful in the optimal design of industrial and engineering equipment, including electronic coolers.

In the present work the amount of entropy produced due to the conjugate heat transfer of power-law fluids during natural convection within the inclined chamber under magnetic field and heat absorption/production is investigated. Outcomes:1-The flow power,the amount of heat transfer and the entropy produced decrease with increasing Hartmann number, decreasing Rayleigh number and increasing the fluid power-law index.2-As the power-law index decreases,the influence of the magnetic field becomes more pronounced.The mean Nusselt number decreases by about 52% for shear thinning fluid and by about 18% for dilatant fluid by increasing the Hartmann number to the highest value.3-To achieve a current with higher power and higher average Nusselt number,the magnetic field can be used non-uniformly,especially TMF1. The larger the Hartmann number, the more pronounced the change in the type of magnetic field applied.The influence of the change in the type of magnetic field applied to the shear thickening fluid is minimal.4-As the thermal conductivity ratio increases, the maximum mean Nusselt number is obtained, in which case the impact of increasing the Hartmann number and the Rayleigh number becomes more pronounced.5-The minimum amount of heat transfer, current strength and magnetic field influence is obtained when the chamber is at an angle of +90 degrees,in which case the average Nusselt number is up to about 82% less than the zero angle.6-The Bejan number increases with increment of heat absorption/production coefficient,increasing Hartmann number, decreasing Rayleigh number and decrement of thermal conductivity ratio,and maximum the Bejan number is obtained at an angle of +90 degrees.

The purpose of this paper is to investigate the heat transfer and entropy generated due to mixed convection of hybrid nanofluid inside the lid-driven semi-oval chamber. The magnetic field is applied uniformly and non-uniformly. The simulation is performed by MRT-LBM and by writing computer code in Fortran language. Effect of Richardson number (0.1, 1 and 10), nanoparticles volume fraction (0-0.06), Hartmann number (0-60), inclination angle of the chamber (-90, 0 and +90 degrees) and type of magnetic field applied (uniform and non-uniform) on the flow formed in the chamber is evaluated. The results show that increasing the volume fraction of nanoparticles increases the flow strength, average Nusselt number, total volumetric entropy and Bejan number and most of the effect is observed for Richardson number 10 and inclination angle +90°. In all cases, increasing the Hartmann number decreases maximum values of streamlines and heat transfer, and this effect decreases with increasing Richardson number. By applying a magnetic field non-uniformly, it can change the flow strength by more than 80% and increase the heat transfer to 35%. Increasing the Hartmann number makes the effect of the non-uniform magnetic field more obvious, and the heat transfer has the largest share in the total volumetric entropy.

the flat solar heating transpired collector can be used for heat buildings and large spaces, industrial applications, and drying of agricultural products. The flow structure and convection heat transfer mechanisms are very important to the air performance of uncovered flat solar heating transpired collector. In these solar air heaters, the air is usually heated by a perforated absorber plate (metal). In this research, copper adsorbent plate has been used and numerical simulation has been performed for mass flow rate (0.007, 0.01, 0.0125, 0.015) kg/s. In order for the simulation to be consistent with the physical reality of the problem, the simulation is three-dimensional, non-continuous with a large computational range and continuous suction. Thermal efficiency, mass flow rate, and outlet temperature parameters were investigated. According to the obtained results, with decreasing mass flow rate, the temperature of the absorber plate and consequently the temperature of the outlet air increases; But increasing the temperature of the absorber plate is more than increasing the temperature of the outlet air. As the mass flow rate increases, the thermal efficiency of the flat solar heating transpired collector increases. The lowest efficiency in mass flow rate is 0.007 kg / s with 66.51 % and the highest efficiency in mass flow rate is 0.015 kg / s with 78.02 %.

In this study, energy and exergy for different parts of a 5 MWe direct steam generation (DSG) solar power plant was analyzed for Yazd city climate. It was observed that the most energy in the condenser and the most exergy losses occurred in the parabolic solar concentrator. To improve the efficiency of the concentrator, this study recommends to preheat the water entering the concentrator with one or more open preheaters in which the extractions of steam from turbine should be optimized by their pressures and mass flow rates. For different cases in which the cycle has up to 4 preheaters, the efficiency of the first and second laws of thermodynamics was investigated. In the case of 4 preheaters, based on obtained results, it was revealed that the efficiency of the first and second laws were 17.2% and 16%, respectively which was a significant increase compared to the case where the cycle had one, two or three preheaters. Therefore, according to the obtained results from the efficiency of the first and second laws as well as the irreversibility of power plant components, the cycle of the present article can be recommended for the city of Yazd.

In the present study, the entropy generated due to the conjugate heat transfer of the hybrid nanofluid inside the K-shaped chamber under magnetic field and uniform heat absorption/generation is investigated. The simulation was performed by writing computer code in Fortran language using the lattice Boltzmann method. Variations in Rayleigh number, volumetric fraction of nanoparticles, Hartmann number, heat absorption/generation coefficient, thermal conductivity ratio, chamber aspect ratio and type of magnetic field applied have been evaluated as the main variables of this study. The findings showed that the flow strength, heat transfer rate and entropy produced could be reduced by applying a magnetic field. A lower reduction of the average Nusselt number is achieved by non-uniform application of a magnetic field. Increasing the heat absorption/generation coefficient due to increasing the set temperature leads to decreasing the mean Nusselt number, which this influence increases with increasing the Hartmann number. Addition of nanoparticles to the base fluid in which the conduction of the phenomenon is predominant, increases the rate of heat transfer. Heat transfer is a function of the ratio of thermal conductivity and Rayleigh number that increasing these two parameters increases the convection effects, and in this case, the effect of increasing the Hartmann number is more pronounced. Increasing the chamber aspect ratio leads to a decline in the mean Nusselt number and entropy production, but the effect of adding nanoparticles is greater in this case. Entropy production decreases with increasing Hartmann number and increases with Rayleigh number and heat absorption/generation coefficient.

The purpose of this work is to investigate the effect of magnetic field direction on heat transfer of Newtonian and non-Newtonian fluids in both uniform and non-uniform forms, with the power-law model by using the multiple relaxation time lattice Boltzmann method (MRT-LBM) with written computer code by Fortran language. The natural convection is created in the two-dimensional cavity with lozenge barrier and is examined in three different temperature boundary conditions. The cold wall of the cavity is investigated in three modes: smooth, curved and diagonal. The results show that increasing the Rayleigh number and decreasing the power-law index and the Hatmann number increase the strength of fluid flow and heat transfer. The smooth design of the wall increases the average Nusselt number by about 30%. Placing the barrier at a constant cold temperature increases the average Nusselt number by 20% on average. The effect of the magnetic field is highest for the smooth wall and lowest for the diagonal wall and this effect decreases with increasing the power-law index. In general, an applied non-uniform magnetic field increases the average Nusselt number by about 10% and increases the flow strength. The effect of wall shape and type of magnetic field applied on shear thickening fluid is negligible. Further reduction of flow strength and average Nusselt number is observed by applying a magnetic field horizontally.

We investigate the phenomenon of electrokinetics in microchannels. Electroosmotic is one of the four electrokinetic effects. Electroosmotic flow (EOF) is caused by the application of an electric field to an aqueous solution. The characteristics of the EOF depend on the nature of the surface potential distribution. EOF in microfluidic systems is limited to low Reynolds. As a result, species mixing in EOF systems is primarily due to diffusion. The surface heterogeneous of the microchannel walls causes the production of micro vortexes in the liquid. In this study, A two-dimensional microchannel is used to study the electroosmotic/pressure driven in Newtonian fluids. The equations governing the fluid flow in a rectangular microchannel are obtained based on the Lagrangian approach and using the density-based weakly compressible smoothed particle hydrodynamics (WCSPH) method. We have analyzed the vortexes due to surface potential heterogeneity and investigated increasing the surface potential on the flow. The results show that increasing the surface potential causes the vortexes to grow and strengthens the velocity and mixing fields more.

In the numerical present study, MHD natural convection heat transfer of non-Newtonian power-law fluid in a two-dimensional enclosure with variable aspect ratio in the presence of heat absorption/generation is investigated by using the lattice Boltzmann method (LBM). The magnetic field is applied to the enclosure in uniform and periodic forms. The vertical wall and curved walls of the enclosure are at constant hot and cold temperature, respectively. The present work is validated with previous studies and the accuracy of the results is ensured. The effect of the Hartmann number, non-Newtonian power-law index, heat absorption/generation coefficient, aspect ratio of the enclosure and the type of magnetic field applied on the nature of flow and heat transfer are studied. The results show that increasing the non-Newtonian power-law index, Hartmann number and the heat absorption/generation coefficient reduce the Nusselt number. By increasing the heat generation/absorption coefficient, aspect ratio and decreasing the non-Newtonian power-law index, the effect of the magnetic field increases. Applying a magnetic field periodically compared to a uniform form leads to an increase of in Nusselt number and flow strength that this effect is greatest for shear thinning fluid and negligible for shear thickening fluid. Increase of Hartmann number and heat absorption/generation coefficient simultaneous leads to further decrease of average Nusselt number. This research can be helpful in the optimal design of heat transfer equipment.

Electroosmotic is one of the four electrokinetic phenomena that is formed by applying an electric field to an ionized electrolyte near the charged dielectric surface. Due to the applying of this electric field change the arrangement of ions within the electrolyte, and eventually a region called the Electric double layer is formed near the surface. The thickness of this layer is approximated by the Debye length. In this study, the Because the Reynolds number in in microfluidic devices is usually very low. Therefore, achieving to sufficient mixing in electroosmotic microchannel flow has been a challenge. For this purpose, a non uniform distribution of surface potential for flow mixing is considered. This type of charge distribution is very efficient for mixing purposes by creating circulations in the microchannel. Lagrangian description is used to solve the governing equations. The method used in this research is the constant density weakly compressible particle hydrodynamics method. In order to improve the mixing, the effect of changing the Debye length has been analyzed. The results show that increasing the Debye length causes smaller vortexes to be produced and mixing efficiency is reduced.

The present study numerically investigates the feasibility of using multiple dielectric barrier discharge multi-DBD plasma actuators inside the surface of geometry as a novel approach for active flow control over a large vertical axis wind turbine. For this reason, the plasma actuator is modeled based on Suzen Model and the results are validated. Then, a computational study is carried out on a commercial large scale vertical -axis wind turbine to examine the effect of the presence of the plasma actuator. The 530G vertical-Axis wind turbine is used as the baseline case. The plasma actuator was applied inside the surface of the blades of turbine and on all their surfaces in a sequential and simultaneous way. Plasma actuator is one of the newest devices in flow control techniques which can delay separation by inducing external momentum to the boundary layer of the flow. It is revealed that the use of multi-DBD actuators could enhance the induced velocity; this affects the pressure distribution and increases the aerodynamic torque. Consequently, an averaged power increase of 3 % was achieved. Possibility of increase in wind turbine power even in a commercial scale large turbine has been proved by flow separation control using the plasma actuation technology. In addition, the application of the plasma inside the surface of the blades will not effect on its performance.

In this paper for the first time, the effect of direction of wall movement on mixed convection in circle quarter porous enclosure with heat absorption/generation is investigated by LBM. The magnetic field is applied to the enclosure in uniform and periodic forms. Mixed convection is caused by the movement of walls at different angles. The results show that increasing the Richardson number, Hartmann number, heat absorption/generation coefficient and decrease the porosity coefficient reduce the average Nusselt number. With fixed all parameters the maximum value of the average Nusselt number is related to the 90 ° velocity angle, in which case the average Nusselt number is about 25% higher.  Increasing the Richardson number reduces the effect of the magnetic field. Periodic applied of a magnetic field results in about 30% more than uniform applied. Increasing the porosity coefficient also increases the effect of the Hartmann number and the angle of wall movement. It is observed that the simultaneous increase of the heat absorption/generation coefficient and the Hartmann number lead to a further decrease of the average Nusselt number.

In this study the strongly coupled method (two-way fluid structural interaction (FSI)) is presented to simulate the membrane wings used in ultralight aircraft. In the present study, numerical modeling is performed by commercial software ANSYS using two separate solvers one for fluid and one for structure. Unlike the one-way method, the two-way coupled method, membrane wing deformation is considered at each time step, which increases the accuracy of the simulation. The membrane wings are made of fabric covering on the naca 2418 plan. fabric is considered to be orthotropic and non-porous. Influence of angle of attack, Young's modulus and thickness of fabric on the aerodynamic coefficients and membrane wing deformation were investigated. All simulations were performed at Re=100000. The results show that increasing the Young’s modulus from 180.25 to 270 MPa reduces the maximum membrane displacement in X and Y direction by 81% and 78%, respectively. Increasing the fabric thickness from 0.4 to 0.6 mm also reduced the maximum displacement of the membrane wings in the X and Y directions by 85 and 80%, respectively.

In the present study, mixing of two fluids of different viscosities in a micro channel with an oscillating curved stirrer was simulated by MRT-LBM and the effect of geometric shape, oscillating speed and amplitude and viscosity logarithmic ratio on mixing efficiency was analyzed. Most researches in this field have studied the mixing of two same fluids but the mixing makes sense when two miscible fluids have different properties. Also in these researches, stirrers in micro channel are considered cylinder or rectangle shape. In this study, a curved stirrer was used for mixing two fluids of different viscosities in micro channel for the first time. The simulation was performed at Re=80 and Sc=10 and NASA/LANGLEY LS(1)-0417 (GA(W)-1) airfoil shape was used for curved stirrer. At the study of geometric shape, results showed that mixing efficiency of two fluids of same and different viscosities in micro channel with oscillating curved stirrer was higher than micro channel with oscillating rectangle stirrer. The results of stirrer oscillating amplitude and velocity survey revealed that increase in Strouhal number causes increase in mixing efficiency on studied oscillating amplitude and Optimum efficiency is on oscillating amplitude 0.5 on all studied Strouhal numbers. Also mixing efficiency decreases with increase of viscosity logarithmic ratio on studied Strouhal numbers and this decrease is noticeable in high Strouhal numbers.

The aim of this research is the simulation of multi-layer flows of the core-annular type in a 2-dimensional channels, in which the Newtonian fluid in the core is surrounded by a viscoplastic fluid of the regularized Bingham type as a lubricant. This simulation is based on the volume of fluid technique and in the mixing regions of the two fluids, the stress is achieved by harmonic interpolation. Flow and concentration equations are discretized spatially by spectral element method. The velocity correction scheme, as a high order algorithm, is developed for splitting the velocity and pressure variables for the viscoplastically lubricated two phase flow. Applying the developed flow considerations leads to a nonlinear equation in the plastic region of the flow, which is solved numerically and is called semi-analytic solution. This solution, along with previously published works, is used to validate the spectral element results. The effect of the main parameters of the flow, i.e. Bingham number, viscosity ratio and core thickness on the pressure drop and un-yielded region thickness is evaluated. The results show that, for constant Reynolds number, the Bingham number is the most effective parameter on the pressure drop and un-yielded region thickness, respect to the core flow thickness and viscosity ratio. Also the profiles of secondary variables, including apparent viscosity and shear stress, across the channel section is presented and show that in the interface of the fluids, there is a difference between numerical and semi-analytic solutions due to the mixing of the two fluids.

In this simulation mixing behavior of two fluids water and ethanol with various density and viscosity mixing in 5 types of T-micromixers numerically has been studied. The five Geometries under research are: 1 and 2 geometries are Multiple T-micromixer with non-aligned inputs in one and two plane respectively, and the 3, 4 and 5 geometries are included Multiple T-micromixer, double T-micromixer and T-micromixer. Simulation has been performed using computational fluid dynamics commerical code of Ansys fluent 18 at Schmidt number of 752.26 for 6 different Reynolds number in range of 1 to 200. In creeping flow range viscosity force and in laminar flow (non-creeping) the chaotic of flow was the main mixing factors for all studied geometry. For double T-micromixer and multiple T-micromixers two and three different types for input fluids respectively investigated and the most efficient mixing type has been specified. Cortes-Quiroz et al numerical results used for validation present investigation. Mixing results compared for specific flow types in double and multiple micromixers with single flow type in T-micromixer. The results show mixing index and pressure drop are function of inputs’ number and position also for geometries with more than two inputs, types of input fluids have effect on these parameters.maximum mixing index which was 0.4878 has been observed using flow 1 in Multiple T-micromixer at Re= 1

In this article, the magnetic field effect on the natural convection heat transfer is simulated via LBM. The vertical wall of the left side of the cavity is at a constant hot temperature, while the vertical wall of the right side of the cavity has three different temperature boundary conditions, 1) constant cold temperature, 2) linear temperature and 3) constant hot temperature. A lozenge-shaped obstacle located in the center of the cavity is examined in four different modes, 1) cold, 2) conducting, 3) adiabatic, and 4) hot. The bottom wall of the cavity is also evaluated in three different slopes. The results show that increasing the slope of the wall and the Rayleigh number by unchanged all the parameters leads to an increase in heat transfer. Also, changing the boundary temperature of the walls and the obstacle can affect the amount of heat transfer. In addition, increasing the strength of the magnetic field reduces the average Nusselt number, which differs in different conditions.