فهرست مطالب maryam moein addini

The positive effect of self-sustained passive oscillations of two flexible vortex generators (VGs) in the naturally air flow of a solar air heater (SAH) is examined in this paper. Two VGs are attached on opposite walls of 2-D channel of the heater, where the turbulent air flows because of the buoyancy effect. The set of continuity, momentum and energy equations for free convection flow and also the equation of motion for elastic solid structure considering a two-way strongly-coupled fluid-solid interaction (FSI) are solved in transient condition by the finite element method (FEM).  Numerical result shows higher performance for SAH with two VGs in comparison with a single winglet and also with clean SAH. Although, the airflow rate decreases about 16% in SAH with two VGs because of the blockage effect of winglets, but 35% improvement in bulk temperature increase along the SAH is seen in comparison to the single VG solar heater. The applied numerical simulation has been validated against experimental and theoretical results of literature and good agreement was found.

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.

This study presents a numerical investigation for laminar mixed convection flow of radiating gases in an inclined lid-driven cavity. The fluid is treated as a gray, absorbing, emitting and scattering medium. The governing differential equations consisting the continuity, momentum and energy are solved numerically by the computational fluid dynamics (CFD) techniques to obtain the velocity and temperature fields. 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 convection and conduction, radiative heat transfer also takes place in the gas flow. For computation of the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM). The effect of lid driven speed, on the thermohydrodynamic behavior of two-dimensional cavity is carried out. Results are shown as contours of isotherms, streamlines and distributions of convective and total Nusselt numbers along the bottom wall of cavity. It is revealed that increasing in Reynolds number causes almost uniform temperature distribution in cavity, especially for 30° and 60° inclination angles.