Abstract
•We consider unsteady mixed convection in a lid driven trapezoidal enclosure.•Bottom wall is heated and concentrated uniformly and non-uniformly.•Mass and heat lines distorted for the higher value of Br at Ri=100.•Mass and heat transfer rate is greater for in case-I than the case-II.•Mass transfer rate is higher than the heat transfer rate in both.
In this paper we concentrate to investigate the double diffusive unsteady mixed convection flow in a trapezoidal enclosure in presence of magnetic field. The bottom wall of the enclosure is heated and concentrated uniformly (case-I) and non-uniformly (case-II) while the top wall is cooled and moved uniformly with a constant velocity. Both side walls are adiabatic and impermeable. The coupled governing equations for this phenomenon is solved numerically using weighted residual based Galerkin technique of finite element method (FEM) for Richardson’s number (Ri=0.1–100) and Buoyancy ratio (Br=−10 to 10) at time τ=1.0. Reynolds number, Prandtl number and Lewis number are fixed at 100, 0.71 and 10 respectively. Streamlines, isotherm lines and iso-concentration lines are used to show the result graphically for velocity, temperature and mass distribution respectively. Nusselt and Sherwood number values are presented graphically to show the heat and mass transfer rate from the bottom surface of the cavity.