Estimation of Spillway Free Jet Trajectory Lengths

by Peter J. Rae, Acres Int Ltd, Niagara Falls, Canada,
Diana Hurdowar-Castro, Acres Int Ltd, Niagara Falls, Canada,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


The design of high head spillways with flip bucket terminal structures must include analysis of the length of the free jet issuing from the spillway. Prototype jet trajectory lengths are acknowledged to be significantly shorter than the theoretical distance determined from the path of a projectile. The effects of air resistance, chute aeration and turbulence on free jets are not reproduced in most Froude scaled model studies of high head spillways and analytical methods are used to estimate the length of the prototype jet trajectory. Examination of surveyed cross sections through prototype scour holes was used to provided indirect confirmation of jet trajectory length for design. The paper reviews published plunge pool scour information and discusses the implied reliability of jet trajectory estimation relationships.

Subject Headings: Spillways | Drag (fluid dynamics) | Scour | Structural analysis | Hydraulic design | Drop structures | Projectile penetration | Load and resistance factor design

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