Author(s): John Finnie
Linked Author(s):
Keywords: Supercritical flow; Bend; Hydraulic model; Water surface slope
Abstract: The behavior of supercritical flow around a bend in a circular conduit is investigated. Physical models of open channels have been built and operated for specific supercritical flows. However, little information is available regarding the behavior of supercritical flow around a bend in a circular conduit. A model consisting of approximately 30 feet of 2.5 inch diameter clear PVC pipe was constructed in the Hydraulics Laboratory of the Buchannan Engineering building at the University of Idaho in Moscow. The lower reach of the model included an in-plane bend of 90 degrees with a radius of 6 feet. Free surface flows corresponding to Froude numbers between 2 and 7 were created. Upstream length was sufficient to create uniform flow upstream of the bend. For each Froude number, the slope of the water surface (in the radial direction) was measured at various distances along the curve. As expected, the bend in the supercritical flow created a steep slope in the cross section of the water surface. However, the transverse water surface slope was not constant throughout the bend. It reduced and changed sign as it progressed around the bend. The oscillations in the water surface slope continued around the bend, with decreasing maximum surface slope and distance between cross sections of maximum surface slope. In a few cases, a section of straight conduit was added beyond the bend. This induced another maximum surface slope which also oscillated and dampened.
Year: 2009