THERMAL RADIATION EFFECT ON TURBULENT FORCED CONVECTION FLOW OVER A BACKWARD FACING STEP IN THE PRESENCE OF PARTICIPATING MEDIA

The effect of radiation on turbulent forced convection flow over a two-dimensional duct with a sudden expansion was studied numerically. The medium is treated as a gray, absorbing, emitting, and scattering. The two-dimensional Reynolds-averaged Navier-Stokes equations, coupled with the energy equation and the turbulence kinetic energy equations, as well as their dissipation rates are solved numerically by the computational fluid dynamics (CFD) techniques to obtain the velocity and temperature distributions in the channel. The AKN low-Reynolds-number model is employed for computation of turbulence fluctuations. The finite volume method is adopted to solve the governing equations, while the integro-partial differential radiative transfer equation is solved by the discrete ordinates method (DOM). The SIMPLE algorithm is used for pressure-velocity decoupling. Along a benchmark problem, the numerical results are compared with some experimental data and good agreement is found. Results are presented for the distributions of bulk temperature and Nusselt numbers by varying the controlling parameters, i.e., radiation-conduction parameter (RC), optical thickness, single scattering albedo, and wall emissivity. Two different thermal boundary conditions are considered and results show that the gas radiation has a significant effect on the heat transfer.