Three-dimensional flow with elevated helicity in driven cavity by parallel walls moving in perpendicular directions

Abstract

The proposed flow in a 3-D cubic cavity is driven by its parallel walls moving in perpendicular directions to create a genuinely three-dimensional highly separated vortical flow, yet having simple single-block cubical geometry of computational domain. The elevated level of helicity is caused by motion of a wall in the direction of axis of primary vortex created by a parallel wall. The velocity vector field is obtained numerically by using second-order upwind scheme and 2003 grid. Helicity, magnitude of normalized helicity, and kinematic vorticity number are evaluated for Reynolds numbers ranging from 100 to 1000. Formation of two primary vortices with their axis oriented perpendicularly and patterns of secondary vortices are discussed. Computational results are compared to the well-known 3-D recirculating cavity flow case where the lid moves in the direction parallel to the cavity side walls. Also results are compared to the diagonally top-driven cavity and to the cavity flow driven by moving top and side walls. The streamlines for the proposed flow show that the particles emerging from top and bottom of the cavity do mix well. Quantitative evaluation of mixing of two fluids in the proposed cavity flow confirms that mixing occurs faster than in the benchmark case.