Time-averaged sub-layer concentration profiles in oscillatory sheet flows |
| |
| Authors: | Yuhai Wang Wenhong Cao Wen Lu Huifeng Liu Gauhu Sun Chonghao Wang Fei Liu |
| |
| Institution: | State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Chegongzhuang West Road No. 20, Beijing 100048, China |
| |
| Abstract: | Although thin on the order of several to tens of millimeters, sheet flows normally comprise a lower pick-up sub-layer and an upper contact-load sub-layer, separated at the bed level (z = 0). The time-averaged concentration profile in the pick-up sub-layer shows a ‘convex upward’ curvature, but ‘concave upward’ shape characterizes the time-averaged concentration profile in the contact-load sub-layer. The time-dependent concentration in the contact-load sub-layer is approximately in-phase with the free stream flow velocity, whereas it is nearly in anti-phase with the free stream flow velocity in the pick-up sub-layer. Two distinct analytical expressions of the time-averaged concentration profiles for the respective sub-layers are proposed. The expressions are validated with detailed observation datasets collected in the Groβer Wellenkanal (GWK) prototype wave flume in Hannover, Germany. The agreement between the predicted and the measured values is excellent. Interparticle collisions in the pick-up sub-layer and convective lifting processes associated with vortex shedding in the contact-load sub-layer are considered responsible for the opposite curvatures and in-phase/anti-phase concentration variations. Both transitional boundary and reference concentration are also elaborated. |
| |
| Keywords: | Sheet flow Sub-layer Time-averaged concentration profile Suspension mechanism |
| 本文献已被 CNKI ScienceDirect 等数据库收录！ |
