Supercritical Bend Flow

Abstract

Supercritical flow in chute bends is considered both theoretically and experimentally. The conventional approach is found to apply to small relative curvature only. The knowledge is extended to large bend numbers, and a design procedure is presented. Supercritical bend flow in the smooth horizontal and rectangular channel is considered. It is found that the maximum standing wave heights are influenced by the bend number, that is, the approach Froude number times the square root of the average relative curvature. Current models are demonstrated to apply for relatively small bend numbers. For modest and large bend numbers, however, the flow pattern is modified. Besides the extreme wave lengths, the generalized surface profiles along either bend wall, the typical velocity fields, and the separation mechanism are experimentally studied. Also, a model for separated bend flow is developed. Photographs are presented that illustrate the uneven distribution of separated bend flow in regard to the cross-sectional area. This study allows a simple and straightforward design of chute bends.