جستجوی مقالات مرتبط با کلیدواژه « dom » در نشریات گروه « مکانیک »

Two-dimensional numerical study of flow and temperature fields for laminar natural convection and radiation in the inclined cavity is performed in the present work. The walls of the square cavity are assumed kept at constant temperatures. An absorbing, emitting, and scattering gray medium is enclosed by the opaque and diffusely emitting walls. The set of governing equations, including conservation of mass, momentum, and energy for fluid flow, is solved numerically by the CFD method, while radiation computation is based on the numerical solution of the radiative transfer equation. The finite volume method has been adopted to solve the governing equations, and the discrete ordinates method (DOM) is used to model the radiative transfer in the absorbing-emitting medium. The effects of Rayleigh number from 103 to 106 and inclination angle in a broad range from 0 to 90o on temperature and velocity distributions and Nusselt numbers are investigated. It was found that the total heat transfer in the cavity is increased under thermal radiation, and variation of inclination angle causes a sweep behavior in the flow pattern inside the cavity.

This paper presents a numerical investigation of the laminar mixed convection flow of a radiating gas in an inclined lid-driven cavity. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The governing differential equations including continuity, momentum and energy are solved numerically by the computational fluid dynamics techniques (CFD) to obtain the velocity and temperature fields. The discretized forms of these equations are obtained by the finite volume method and solved by using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides convection and conduction heat transfer, radiation also takes place in the gas flow. For computing the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM). The streamline and isotherm plots and the distributions of convective, radiative and total Nusselt numbers along the bottom wall of the cavity are presented. In this work, an attempt is made to investigate the hydrodynamic and thermal behavior of the mixed convection flow of a radiating gas at different values of the cavity inclination angle. The numerical results reveal that the variation of inclination angle causes a sweep behavior in the flow pattern inside the cavity. Besides, it is found that the value of radiative Nusselt number along the heated wall has a decreasing trend when the medium optical thickness is increases. Comparisons between the present numerical results with those obtained by other investigators in the cases of conduction-radiation and pure convection systems show good consistencies.

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 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 radiation-conduction parameter and wall emissivity.

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.

This article deals with a simple Cartesian practical method named blocked-off procedure to study the steady state combined conductive-radiative heat transfer in two dimensional irregular geometries. Using this technique, both straight and curvilinear boundaries can be treated. The finite-volume method is employed to solve the energy equation and the discrete ordinates method (DOM) is used to solve the radiative transfer equation (RTE) to obtain the temperature and radiative-conductive heat flux distributions inside the participating medium. The walls of enclosures are opaque, diffuse and gray with specified temperatures. The medium was considered to be absorbing-emitting and isotropic scattering with variable thermal conductivity. In the case of constant thermal conductivity, results have been compared with those reported in the literature. The major part of this work is to investigate the effects of variable thermal conductivity on the thermal characteristics of radiative-conductive systems.

In the current work, two-dimensional simulations are presented for incompressible laminar mixed convection flow of a radiating gas over a recess including two backward and forward facing steps in a vertical duct. The continuity, momentum and energy equations for fluid flow are solved by the computational fluid dynamic (CFD) techniques. The fluid is treated as a gray, absorbing, emitting and scattering medium. For computation of the radiative term in the energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM). The effects of Grashof number, radiation-conduction parameter and ptical thickness on heat transfer behavior of the system are studied.