Predicting Impact Velocities of Developed Jets

• Published in: Water international Vol. 24; no. 3; pp. 255 - 265
• Main Authors: Lewis, Todd M., Abt, Steven R., Wittler, F. Rodney J., Annandale, George W.
• Format: Journal Article
• Language: English
• Published: Carbondale, IL Taylor & Francis Group 01-09-1999; International Water Resources Association
• Subjects: dam safety; Dam stability; developed jet; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Engineering geology; Exact sciences and technology; free-falling jets; impact velocity; scour; undeveloped jet; instruments; physical models; simulation; safety; mathematical models; erosion; foundations; impacts; velocity; dams; stability; laboratory studies
• ISSN: 0250-8060; 1941-1707
• DOI: 10.1080/02508069908692169

Dam overtopping often results in the erosion of foundation and abutment materials. To quantify erosion potential, the jet impact velocity at the plunge pool interface must be estimated. Regións of the overtopping jet trajectory through free-fall are termed undeveloped (compact) and developed (individual particles). A physical model was constructed to simulate the developed region of a free-falling jet and to measure the impact velocity of developed jets. The equation derived for estimating the impact velocity of an undeveloped jet (Ervine and Falvey, 1987) was applied to the developed portion. The undeveloped jet estimation equation significantly overestimated the impact velocity of the developed jet. A drag expression was formulated and appended to the undeveloped equation resulting in a new equation, referred to as the Dimensional Equation Technique. The Dimensional Equation Technique was used to estimate developed jet impact velocities to within ± 4 percent.