Lower Monumental Spillway Hydraulic Model Study
Abstract
A 1:40 Froudian Scale model was used to investigate the hydraulic performance of the Lower Monumental Dam spillway, stilling basin, and tailrace for dissolved gas reduction and stilling basin apron scour. The model reproduced a 2-1/2 bay section of the spillway and portion of the nonoverflow section between the spillway and navigation lock. Performance characteristics of two spillway deflectors were evaluated. The existing deflector (12.5 ft long horizontal with small fillet radius for transition from spillway to deflector) was recommended at el 434.0 because of its slightly wider tailwater range for operation in skimming flow. However, for fish passage over the deflector, the Type I deflector (12.5 ft horizontal with lS-ft radius transition) can likely be adopted with little degradation in dissolved gas uptake. Loadings on the deflector were estimated with pressure measurements on the horizontal and vertical faces. Instantaneous cavitation pressures were measured on the vertical face of the deflector due to flow separation. Only minor cavitation damage has been observed at other spillway deflectors, and thus, significant damage is not expected. Pressure measurements on the stilling basin flow show potential uplift pressure as high as 3,300 lb/ft. If these pressures have a pathway beneath the stilling basin apron, significant uplift force could result, ultimately causing a catastrophic failure of the apron.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2003
- Accession Number
- ADA417964
Entities
People
- Laurin I. Yates
- Steven C. Wilhelms
- Thomas E. Murphy Jr.
Organizations
- Engineer Research and Development Center