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In this work, the three-dimensional free convection flow in a modeled room was studied for various Grashof numbers (Gr = 2 × 104 and 2 × 105) and Hartmann numbers (Ha = 0 and 100) by the lattice Boltzmann method (LBM), and the effect of magnetic field on the flow and temperature field was investigated. For consideration of the effect of magnetic field on particle behavior in a three-dimensional modeled room, 50,000 particles with sizes of 1 and 10 μm were injected into the room. The number of deposited particles on the different walls of the room was obtained, and it was observed that by increasing the Grashof number, the total number of deposited particles for both particle sizes and both Hartmann numbers enhances. Moreover, for Ha = 100, the number of deposited 10 μm particles on the walls increases. Therefore the number of suspended particles in the modeled room decreases, which is environmentally desirable. However, the number of deposited 1 μm particles on the walls decreases in the presence of the magnetic field. Furthermore, it was found that the gravity force has a significant effect on the particle deposition, as the number of deposited 10 μm particles on the floor is much larger than 1 μm particles. [ABSTRACT FROM AUTHOR]

New numerical approach has been selected for simulating magnetic force and radiation influences on alumina transportation within a permeable medium. To enhance characteristics of working fluid, we choose Al2O3–water with various shapes of nanoparticles. Various amounts of radiation, magnetic force and buoyancy have been considered to show their impacts on nanoparticles transportation. Brownian motion influences on working fluid thermal conductivity and viscosity were involved. Outcomes prove that convection decreases with augment of magnetic forces. Considering radiation can increase Nusselt number. [ABSTRACT FROM AUTHOR]

This research deals with the study of the irreversibility of three-dimensional mixed convection flow in an inclined duct with step. To reach this goal, an analysis of entropy generation is carried out according to the second law of thermodynamics. The effects of buoyancy force on the flow irreversibility are analyzed with all details. The results show that the values of entropy generation number and Bejan number are intensively dependent on the Grashof number and duct inclination angle, so that the effects of Grashof number on the mentioned parameters are much higher for the vertical ducts. [ABSTRACT FROM AUTHOR]

In this paper, a numerical algorithm is presented to simulate the three-dimensional transient incompressible flow using a meshless local Petrov-Galerkin (MLPG) method. In the proposed algorithm, the forward finite difference (FFD) and MLPG methods are employed for discretization of time derivatives and solving the Poisson equation of the pressure, respectively. The moving least-square (MLS) approximation is considered for interpolation, while the Gaussian weight function is used as a test function. Furthermore, the penalty approach is applied to satisfy the boundary conditions. Moreover, in two examples, the accuracy and efficiency of this approach is compared with the exact solutions. [ABSTRACT FROM AUTHOR]

In this research, the coupling between non-gray radiation and separation convection flow in a duct is investigated numerically. Distributions of absorption coefficients across the spectrum (50cm-1 < η < 20000cm-1) are obtained from the HITRAN2008 database. The full-spectrum k-distribution method is used to deal with the non-gray part of the problem, while the gray radiation calculations are performed using the Planck mean absorption coefficient. To find the divergence of radiative heat flux distribution, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The effects of radiation-conduction parameter, scattering coefficient and wall emissivity on thermal behaviors are investigated for both gray and non-gray mediums. In addition, the results of gray medium are compared with non-gray results as a real case. The results show that in many cases, use of gray simulations is not acceptable and leads to significant errors, especially in non-scattering medium with high values of radiationconduction parameter and wall emissivity. [ABSTRACT FROM AUTHOR]

In this paper, the effects of baffle on thermal characteristics of combined convection-radiation heat transfer in laminar flow adjacent to an inclined backward facing step (BFS) in a horizontal duct are investigated. A baffle is mounted on the top wall of channel downstream side of step. In this study, the fluid is treated as a gray, absorbing, emitting and scattering medium; therefore, in the energy equation besides the convective and conductive terms, radiation term is also presented. The radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the divergence of radiative heat flux distribution inside the radiating medium. The blocked off method is employed for both fluid mechanic and radiation problems to simulate the presence of both step and baffle. The effects of height, width and location of baffle in channel and also the effects of radiative parameters on the fluid flow and heat transfer are investigated by plotting the variations of streamlines, Nusselt number and mean bulk temperature along the flow. It is revealed that, baffle and radiative parameters have great influences on flow and the thermal behaviors of systems with combined convection-radiation heat transfer. [ABSTRACT FROM AUTHOR]

This study presents a numerical analysis of three-dimensional laminar forced convection flow of a radiating gas over an inclined backward-facing step in a rectangular duct under bleeding condition. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The three-dimensional Cartesian coordinate system is used to solve the governing equations which are the conservations of mass, momentum, and energy. These equations are solved numerically using the computational fluid dynamic techniques to obtain the temperature and velocity fields, while the blocked-off method is employed to simulate the incline surface. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides the convective and conductive terms in the energy equation, the radiative term also presented. For computation of this term, the radiative transfer equation is solved numerically by the discrete ordinates method to find the divergence of radiative heat flux distribution inside the radiating medium. By this numerical procedure, the role of radiation heat transfer on convection flow of a radiating gas which has many engineering applications (for example in heat exchangers and combustion chambers) is studied in detail. Beside, the effects of bleeding coefficient, albedo coefficient, optical thickness, and the radiation–conduction parameter on heat transfer behavior of the system are investigated. Comparison of numerical results with the available data published in the open literature shows a good agreement. [ABSTRACT FROM AUTHOR]

This research work presents a numerical investigation of entropy generation in laminar forced convection of gas flow over a recess including two inclined backward and forward facing steps in a horizontal duct. Although the flow in this type of geometry has many applications in thermal systems, but this type of convection flow has not been analyzed by any investigator. For calculation of entropy generation from the second law of thermodynamics in a force convection flow, the velocity and temperature distributions are primary needed. For this purpose, the twodimensional Cartesian coordinate system is used to solve the governing equations using the computational fluid dynamic techniques, while the Blocked off Method is employed to simulate the inclined surfaces. The numerical results are presented graphically and the effects of step inclination angle, recess length and Reynolds number on the distributions of entropy generation number, Bejan number and total entropy generation are investigated. [ABSTRACT FROM AUTHOR]

This research work presents a numerical investigation of laminar forced convection of gas flow over a recess including two backward and forward facing steps in a horizontal duct subjected to bleeding condition. The two-dimensional Cartesian coordinate system is used to solve the governing equations which are conservations of mass, momentum and energy. These equations are solved numerically using the CFD techniques to obtain the temperature and velocity fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. The numerical results are presented graphically and the effects of bleeding coefficient and recess length on the flow and heat transfer behaviors of the system are investigated. Comparison of numerical results with the available data published in open literature shows a good consistency. [ABSTRACT FROM AUTHOR]

During the past decades, the relationship between various psychological parameters had been studied in detail. However, the dependency structure of correlated parameters was rarely investigated. Knowing the dependence structure helps in finding the probability matrix of the interaction between the parameters. In this research, a novel approach was introduced in psychological analysis using copula functions. For this purpose, the self-esteem and anxiety of 141 university students in Iran were extracted using the Coopersmith Self-esteem Inventory and the Zang Anxiety Scale. Then the dependence structure of self-esteem and anxiety were established using copula functions. The Frank copula achieved the best fit for the joint variables of self-esteem and anxiety. Finally, the probability matrix of different classes of anxiety, taking into account self-esteem classes, was extracted. The results indicated that poor self-esteem leads to severe or very severe anxiety, with more than 98% probability, while strong self-esteem may lead to normal and mild anxiety, with about 80% probability. It can be concluded that the method was promising, and that copula functions can open a window to the dependence structure analysis of psychological parameters.