Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2016
Publication Date: N/A
Technical Abstract: Early research on stepped chutes focused on steep gravity style stepped chutes. Today, the research trend has shifted to stepped chutes applied to more moderate slopes like those for aging embankment dams. Research contributions have been made on hydraulic properties of stepped chutes including air entrainment inception point, air-water flow properties, and energy dissipation. Research has also extended to design properties (i.e. Froude number, sequent flow depth, and tailwater) for stilling basin design associated with stepped chutes. The USDA-ARS Hydraulic Engineering Research Unit (HERU) has conducted a multi-year, large-scale physical model study on stepped chutes. The study was conducted for a broad range of step height to critical flow depth ratios and chute slopes. The objectives of the study were to evaluate the step height to critical flow depth ratio and the chute slope effect on the surface inception point, clear water and bulked flow depth, air concentration, and energy coefficient. Additional testing focused on training wall and stilling basin design requirements. Relationships for air concentration, clear water flow depth, bulked flow depth, and energy coefficient were developed. Many researchers have indicated that the step height to critical flow depth does not play a role in determining these flow properties; however, the findings of this study along with supporting data from literature showed these relationships are a function of (1) the length from the downstream edge of the broad-crested weir to the point of interest to the characteristic length from the downstream edge of the broad-crested weir to the free-surface inception point ratio, (2) the step height to critical flow depth ratio, and/or (3) the chute slope. Further research indicates that the USBR stilling basin design criteria is applicable for basin design for stepped chutes.