Dam Foundation Erosion Study: The Design of a Sidewall Orifice for Simulation of a Free Trajectory Overtopping Jet

by R. J. Wittler,
S. R. Abt,
T. L. Lewis,
J. F. Ruff,
K. Adhya,

Document Type: Proceeding Paper

Part of: North American Water and Environment Congress & Destructive Water


This paper describes the design of a sidewall discharging orifice for simulation of a free trajectory overtopping jet. A sidewall orifice discharges through the sidewall of a pipe. The orifice performance is a critical aspect of the similitude necessary for modeling erosion and scour in the abutment and foundation areas of dams. Between April and July, 1994, the Dam Foundation Erosion Scale Model Study Team designed and tested the orifice and manifold assembly in the scale model facility at Colorado State University. The variables include discharge, diffuser angle, diffuser hole area, orifice blade opening and setting, pressure in the supply pipeline, and head tap readings. The performance of each configuration has two subjective and one objective ratings, jet uniformity, skewness, and velocity distribution. The subjectivity comes from the judgment of the Principal Investigator, Scale Model Study Team Leader, and study consultants who witnessed all of the tests. The velocity distribution was measured with a Pitot tube at the vena-contracta of the jet.

Subject Headings: Dam foundations | Scale models | Foundation design | Wave overtopping | Velocity distribution | Piping erosion | Diffusion

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