Author(s): Vesselina Roussinova; Ram Balachandar; Panneer Selvam
Linked Author(s): Vesselina Roussinova, Ram Balachandar
Keywords: No Keywords
Abstract: In this paper, the turbulent flow past a train of rib elements located in an open channel is examined at three depths of flow. The rib elements are composed of twodimensional square rods spanning the width of the channel and are located throughout the length of the flume. The characteristics of the flow are examined at two different rib separations (p/k = 9 and 18; p is the pitch and k is the rib height) conforming to the classical definition of k-type roughness. The ratio of the rib height (k) to the depth of flow (d) varies from 0.10 to 0.15 and falls in the category of large roughness. For each of the six test conditions, two-dimensional laser Doppler velocimeter (LDV) measurements were obtained in the middle of the cavity formed between successive elements. From these measurements, information regarding the mean velocities, turbulent intensities and Reynolds shear stress were obtained. At shallow depth, the rough bed flows show substantial increase in turbulent intensities and Reynolds shear stress compared to the reference flow on a smooth bed. Quadrant analysis was used to investigate the effect of flow depth on the turbulence structure in the outer layer. For the rough bed shallow flow, the ratio of the shear contribution of sweep to ejection events are very different from that obtained on the smooth bed. For the larger depth, this difference diminishes in the outer region.
Year: 2009