Techniques for analyzing flow velocity profiles for streams where the flow depth is less than 1 m should be employed with caution. The two procedures for calculating flow resistance based on the logarithmic law, (1) mean and maximum velocity determinations and (2) intereept evaluation of log depth – velocity plots, should yield the same results for the various resistance coefficients and shear stress values, but they do not. The former procedure generally predicts higher values than the latter and is recommended for shallow streams where the field data were collected. For a 3.8 cm diameter flow sensor, the minimum distance from a boundary to the position of maximum velocity for a good velocity profile appears to be roughly 15–20 cm.The fluid shear stress values for ice covers on this shallow stream range from 0.1 to 17 Pa, depending upon ice type and duration of the cover. The shear stress under frazil ice slush showed a drop of about one tenth the initial value over a 2-week period at one location. The measured division of flow velocities about the maximum velocity associated with the bed and ice boundaries indicated that the mean velocities were not equal but often differed by as much as 25–30%, generally being higher in the section associated with ice, i.e., a rougher ice boundary.The most consistent method of determining the resistance coefficients was to define the cross-sectional shape of the river and ice cover accurately, subdivide the flow areas, use the mean velocity data calculated from the velocity profiles, and then compute the resistance values accordingly. The sensitivity of the roughness coefficient is discussed in terms of its impact on determining the total stage of an ice-covered river.
Level ire This report describes the development of a river ice prow to be attached to a towboat for opening ice-free navigation channels or for ice management in the vicinity of the locks and dams on the northern rivers of the United States (Illinois, Ohio and Upper Mississippi Rivers). Following a literature survey, the basic concept of the prow was selected to minimize construction and maintenance costs. Three successive models were constructed and tested in level ice in the CRREL Test Basin to optimize the prow's performance from the points of view of resistance and maneuverability in level ice. Test results are presented and discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.