YANG Kai-lin

State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China

Abstract: The composite roughness of the ice covered flow is a key parameter to determine the relationship between the flow and water stage. This paper presents a generalized formula for the composite roughness of ice covered flows by analyzing the relationship among Manning roughness, section-averaged water velocity and wetted perimeter. Based on the generalized formula, the influence of the velocity coefficient a on the composite roughness of the ice covered flows in rectangular channels is studied by considering the distribution of water velocities. Meanwhile, in order to understand the scope of application to them, Einstein formula, Belokon - Sabaneev formula and Larsen formula are compared with the generalized formula systematically. The results show that for the rectangular open channal with small kreadth-depth ratio b/H, the composite roughness computed by Einstein formula approximate closest to that by the generalized formula, and the composite roughness obtained by both Belokon - Sabaneev formula and Larsen formula deviate for from that by the generalized formula in many cases.

Key words: generalized formula; composite roughness; ice cover; open channel and distribution of water Velocity

Published in: Journal of Hydraulic Engineering, Vol. 45, No. 10, 2014