Numerical Study of the Flow Structure and Transport in a Two-Dimensional Channel With Oscillating Periodic Cavities and a Bounding Top Wall

The dynamics of the flow in a two-dimensional channel with an arrangement of periodic cavities in an oscillating lower bounding wall and a confining top wall is studied numerically in this paper. The open-source CFD code, OpenFOAM v.2.2.2, based on the Finite Volume method is used to solve the problem. The flow dynamics is studied with respect to variations in the location of the confining top wall (non-dimensionalized with the Stokes layer thickness z/δ), cavity-size-based Reynolds Number (Re_d) and the ratio of the Stokes Layer Thickness to the Cavity Size (δ/d). This is an extension of work done for a previous paper [20]. The evolution and transport of vortex structures in the vicinity of the are presented over the oscillation cycle time by means of instantaneous streamline plots. The effect of the location of the confining top wall on the flow structure is presented in some detail by comparison of the evolution of the streamlines to a case where the top wall is absent. The transfer of fluid mass in and out of the cavity is shown to be strongly dependent on the Re_d and the z/δ (for the same Re_d, smaller the z/δ, lower is the mass transfer efficiency).