中文摘要：

以Reynolds平均的Navier-Stokes紊流方程为基础，提出了冰盖河渠恒定流的水深平均流速的横向分布准二维模型，该模型包括了河渠流动的一些关键三维紊流因素，不仅适用均匀流和非均匀流，而且适用于明流和断面部分冰封的流动。建立了综合阻力系数 fd 与河床糙率系数nb 和冰盖糙率系数ni 的函数关系，其中nb 和ni 可以是常数，也可以是横坐标 y 的函数。典型冰盖梯形明渠的算例表明，本文模型具有足够的计算精度，同时计算明流无因次涡流黏度λ的方法也适用于冰盖下流动。

英文摘要：

Based on the Reynolds averaged Navier-Stokes equations,a quasi-two dimensional model is pre-sented to determine the lateral distribution of the depth-averaged velocities in steady flows in ice-covered channels. The model, including some key factors on the three dimensional turbulent flows, can be used to simulate not only the steady uniform flows and non-uniform flows, but also free flows and partially-covered flows. For the composite friction factor fd, a formula is establishes that is involved in the lateral ordinate y, the local riverbed roughness coefficient nb and local ice cover roughness coefficient ni. At last, several typical examples are given. The results illustrate that the model presented herein is satisfactory in accura-cy,and that the formula for the dimensionless eddy viscosity in free flows in open channels is also applica-ble to the flows under ice cover.