Similarity of the velocity profile in geometrically distorted flow model

A method is presented to measure the depth-averaged horizontal velocity in distorted physical models, i.e., the depth-averaged horizontal velocity can be equivalent to a point velocity measured at approximately 0.6h below the water surface (h is the water depth). Further a scale for the Chézy coefficient in distorted models is deduced, and the velocity distributions in the vertical in prototype and distorted models are analyzed. By comparing data of the vertical variation of the horizontal velocity measured in a physical distorted model (with distortion ratio of 4.0) with prototype data, inaccuracies via the one-point method, the three-point method and the five-point method are analyzed. It is concluded that it is more accurate to measure the depth-averaged velocity via the three-point method than via the one-point method in the distorted model. What's more, the point velocity at 0.6h below the water surface approximates the depth-averaged velocity in the distorted physical model and the one-point method is proposed to be used in practice.