Experimental investigation of the flow characteristics beneath partial ice covers

In northern climates where water bodies are subjected to sub-freezing temperatures for part of the year it is important to know how the presence of ice impacts the flow characteristics of channels. While many studies have been conducted in channels that are fully open or completely covered with ice, little is known about the hydraulic characteristics of channels with only a partial cover. The goal of this study was to examine the impact of border ice on the discharge and corresponding streamwise velocity distribution in a channel. Using acoustic Doppler velocimetry, detailed three-dimensional velocity measurements were collected in a fully developed cross section of a rectangular flume under steady flow conditions with a symmetrical ice cover extending from both walls. The influence of different extents of partial ice coverages and different Froude numbers was explored. The partial ice cover was found to impact the flow distribution within the channel and a classification system was developed to divide the channel cross-section into open, transitional and covered sections. Partial ice coverage extent was found to have a relative width of transition to be consistent while increasing Froude was found to produce a smaller transition region. Boundary shear stress distributions on the boundaries were examined and a detailed analysis beneath the ice cover is presented. The presented data set represents the most thorough experimental examination of flow characteristics beneath a partial ice cover.