Turbulent flow with wavy permeable boundaries

Abstract

The effects of a wavy permeable boundary on turbulent flow are investigated theoretically and experimentally, mainly in terms of the pressure distribution along the wavy boundary and the friction factors. A simplified theoretical analysis based on potential flow theory and a linear Darcy equation shows that the perturbations of the flow field have a phase shift relative to the wavy surface and that, owing to this phase shift, there results a net form resistance on the wavy surface. Experiments were conducted in two pipelines with different sizes of granular material lining the inside of the pipe walls. The diameter of the porous conduits varied sinusoidally. The experimental results show that there is a phase shift between the boundary wave form and the pressure distribution and that friction factors increase with Reynolds number even though the flow is within the normal fully rough regime.