Combined double-diffusive convection and radiation in a square enclosure filled with semitransparent fluid

A 2D numerical assessment of coupled double diffusive convection and volumetric radiation in a differentially heated square enclosure filled with a gray fluid participating in absorption, emission and nonscattering is carried out. Temperatures and concentrations are imposed at the vertical walls, whereas the horizontal walls are insulated and impermeable. All cavity walls are assumed to be opaque, diffuse and gray. The governing equations are solved by a hybrid scheme with multiple relaxation time lattice Boltzmann (MRT-LBM) and finite difference method (FDM). The velocity field is computed by D2Q9 MRT model while the temperature field is determined by resolution of the energy equation using FDM. The radiative source term in the energy equation is calculated by the discrete ordinates method (DOM) with S8 quadrature. A parametric study illustrating the influence of the buoyancy number (N) and the wall emissivity (εi) on the flow field and the heat and mass transfer is performed. Results are presented in terms of isotherms, streamlines, iso-concentrations, Nusselt and Sherwood numbers. Generally the isotherms and iso-concentrations are inclined in the core cavity, the flow is more stabilized in presence of cooperating flow case but opposing flows are found to be a catalyser of the multi-cellular structures.

► A coupled study of double diffusive convection and radiation was carried out.
► A MRT Lattice Boltzmann and finite difference methods are used.
► The radiative source term is evaluated by the discrete ordinates method (DOM).
► The radiation accelerates the boundary layer and maintains the cavity core stagnant.
► The fields of temperature and concentration are altered, especially by creating a structure with tilted iso-values.