BOUNDARY SHEAR DISTRIBUTION AROUND A CURVE IN A LABORATORY CANAL.
Progress rept. no. 1,
BUREAU OF RECLAMATION DENVER COLO
Pagination or Media Count:
Boundary shear distribution determined from hydraulic measurements in a rigid boundary trapezoidal laboratory canal showed that the highest boundary shear occurred on the inside bank at the upstream end and on the outside bank at the downstream end of the curve. Knowledge of how boundary shear varies around a curve and the location of its high and low areas will be helpful in understanding how to reshape a canal-bend cross section to provide maximum stability and in reducing maintenance costs on earth canals. The 50-ft-long by 6-ft-top-width test canal had a 16-ft-radius cururve that turned a 15-deg angle with the channel centerline. Instrumentation included a Preston tube for boundary shear measurements, a Prandtl tube for velocity measurements, a point gage for water surface profiles, and a differential pressure transducer connected to a direct-writing electrical recorder for pressure measurements. Data were taken at 10 stations located upstream from, in, and downstream from the curve for 1 flow condition--discharge 2.85 cfs and depth 0.75 ft. Test results are given in graphs, drawings, and photographs showing boundary shear distribution throughout the tested reach, and velocity contours and transverse water surface profiles att 10 stts stations. In addition to the physical data, the study showed conclusively that boundary shear can be measured with a Preston tube and that shear distribution can be determined in a laboratory facility. Author