Effects of the Bottom Permeability and Particle Suspension on the Development of Turbulence Under Oscillating Flows

Abstract

 The effects of the bed conditions on a velocity field under an oscillating flow were experimentally investigated by visually measuring the flow fields with various bed conditions; (1) flat bottom, (2) movable granular bottom and (3) fixed permeable bottom. The flows over the granular and permeable bottoms are free from the ‘non-slip’ condition, which can induce attenuation of the bottom shear stress and generation of turbulence under the bottom. It was confirmed that the boundary-layer thickness and vorticity over the bottom decreased on the permeable and movable bottom conditions. Suspension of the bottom particles was found to contribute to transport turbulent energy to the entire flow field.