Author(s)

H. Gotoh, Y. Yasuda & I. Ohtsu

Abstract

Undular hydraulic jumps in sloping rectangular channels have been experimentally investigated. The upper limit of the inflow Froude number for the formation of an undular jump depends on the channel slope; if the channel slope is steeper than the critical slope. The streamwise changes of the surface profile, the bed pressure head, and the bed velocity in undular jumps have been characterized by the channel slope. The effects of channel slope on the wave height, the wave length, and the amplitude of undular jumps have been shown. Also, surface profiles of undular jumps have been compared with theoretical results proposed by Grillhofer and Schneider. The applicability of the theoretical results is discussed. Keywords ：undular jump, hydraulic jump, open channel flow, channel slope. 1 Introduction The undular jump is a well-known transitional phenomenon from supercritical to subcritical flows with undulations of water-surface. The undular jump often occurs at the downstream of low drop structures or in a transitional region from steep to mild sloping channels. Ohtsu et al. [1-3] have shown that the flow conditions of undular jumps in horizontal rectangular channels are characterized by the inflow Froude number, the thickness of the boundary-layer at the toe of jump, aspect ratio, and Reynolds number. Also, Ohtsu et al. [1-3] have classified the flow conditions of undular jumps, and have clarified the hydraulic conditions for undular jump formations. But, there are few information for the effect of channel slope on the undular jump formation. For design purpose, it is necessary to know the effect of channel slope on characteristics of undular jumps.

Keywords

undular jump, hydraulic jump, open channel flow, channel slope.