Estimation of Mean Velocity for Flow Under Ice Coverby Martin J. Teal, (M.ASCE), WEST Consultants, Inc, Carlsbad, United States,
Robert Ettema, (M.ASCE), WEST Consultants, Inc, Carlsbad, United States,
Abstract: Methods of estimating mean velocity in a vertical from point velocity measurements are compared for an ice-covered channel. The comparison is based on velocity profiles obtained from a laboratory flume, a numerical model, and several rivers. The profiles are representative of flows subject to various combinations of bed and ice-cover conditions. The numerically generated profiles use a two-parameter power law to model the vertical distribution of streamwise velocity in ice-covered flows. The velocity bias, defined as the percent error in estimating the average streamwise velocity by using a few point measurements instead of the entire vertical velocity profile, was calculated for several methods. The methods include those currently used by the United States Geological Survey and the Water Survey of Canada and proposed new methods. The recommended method is the so-called two-point method in which velocity measurements at 0.2 and 0.8 of channel depth are averaged to obtain an estimate of the mean velocity. The accuracy of the estimate will be enhanced if a coefficient of 0.98 is applied to the two-point method.
Subject Headings: Ice | Fluid velocity | Velocity profile | Channel flow | Numerical models | Fluid flow | Flow measurement | Flumes | North America | United States | Canada
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