Turbulent Structure in Open Channel Flow
This thesis investigates the effects of pressure gradient and roughness on the mean and turbulence characteristics in non-uniform open channel flow. The flow and turbulence structure over three successive beds with accelerating, near uniform (near zero pressure gradient) and decelerating flow sections were investigated using a two-component laser Doppler velocimetry. The Clauser chart method was considered for evaluating the friction velocity. Inspection of the velocity profiles confirms existence of the overlap region for all flow cases. The upstream condition emanating from the accelerating flow section affects the turbulence characteristics in the near zero pressure gradient section. The outer layer of the velocity distribution of the decelerating section was strongly affected by the pressure gradient, where a large wake was noted. In the outer layer, higher turbulence intensities were noted for the adverse pressure gradient flow. The combined effects of the pressure gradient and roughness on turbulence quantities were further investigated.