TURBULENCE MODULATION BY WALL PERMEABILITY IN A WALL-BOUNDED FLOW

Abstract

 A series of direct simulations of a fully-developed turbulent flow along a mesh-screen type permeable plate whose geometrical property is systematically changed is performed to identify the effect of wall permeability on wall-bounded turbulent flows. The present system includes as two extreme limiting cases the classical impermeable channel flow and the perfectly-permeable channel flow of Yokojima (J. Phys. Soc. Jpn. 80 (2011) 033401), which have an identical solution in the laminar state. The numerical experiment demonstrates that, by increasing the porosity of the plate or by decreasing the pore size, the coherent structures visualized near the boundary show a qualitative transition from the streamwise vortices ubiquitous in a wide variety of wall-bounded flows to thin vortical structures elongated to the transverse direction and the flow resistance is increased. These findings are in good accordance with those observed in the perfectly-permeable channel flow. It is also found that the drag is closely associated with the blowing/suction intensity through the mesh screen.