Structure of Turbulence in Compound Channel Flows

Abstract

The structure of turbulence in compound channel flows is examined in a laboratory study. Shear stresses and turbulence intensities are measured in a channel comprised of a deep central section flanked on either side by wide shallow berms (flood plains). The study concerns the nature of turbulence in the mixing regions separating the deep and shallow zones. Also studied is the mixing region's effect on the compound flow field for both “wide” and “narrow” channel conditions. Under “narrow” channel conditions the mixing process extends to the center of the main channel flow field; however, under “wide” channel conditions, the central region is not affected and observed turbulence levels at the center of the main channel are in close agreement with theoretical values for a two‐dimensional flow field. Apparent shear stress at the vertical main channel‐flood plain interface was measured directly and compared favorably with estimated values based on momentum considerations.