Numerical simulation of unsteady mixed convection in a driven cavity using an externally excited sliding lid

A numerical investigation of unsteady laminar mixed convection heat transfer in a lid driven cavity is executed. The forced convective flow inside the cavity is attained by a mechanically induced sliding lid, which is set to oscillate horizontally in a sinusoidal fashion. The natural convection effect is sustained by subjecting the bottom wall to a higher temperature than its top counterpart. In addition, the two vertical walls of the enclosure are kept insulated. Discretization of the governing equations is achieved through a finite element scheme based on the Galerkin method of weighted residuals. Comparisons with previously reported investigations are performed and the results show excellent agreement. Temporal variations of streamlines, isotherms, and dimensionless drag force, and Nusselt number are presented in this investigation for various pertinent dimensionless groups. Fluid flow and heat transfer characteristics are examined in the domain of the Reynolds number, Grashof number and the dimensionless lid oscillation frequency such that: 10² ≤ Re ≤ 10³, 10² ≤ Gr ≤ 10⁵ and 0.1 ≤ π{variant} ≤ 5. The working fluid is assigned a Prandtl number of 0.71 throughout this investigation. The obtained results reveal that the Reynolds number and Grashof number would either enhance or retard the energy transport process and drag force behavior depending on the conduct of the velocity cycle. Moreover, relatively small lid oscillation values are found to constrain the lid associated motion to a shallow depth from the sliding lid plane.