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Title:	Powerhouse intake gate catapult study, Big Bend Dam, South Dakota, and Stockton, Harry S. Truman, and Clarence Cannon Dams, Missouri : hydraulic model investigation
Authors:	United States. Army. Corps of Engineers. St. Louis District. United States. Army. Corps of Engineers. Kansas City District. United States. Army. Corps of Engineers. Omaha District. George, John F. Pickering, Glenn A.
Keywords:	Big Bend Dam Harry S. Truman Dam Clarence Cannon Dam Stockton Dam Hydraulic structures Electric power plants Intake structures Gates South Dakota Missouri Design
Publisher:	Hydraulics Laboratory (U.S.) Engineer Research and Development Center (U.S.)
Series/Report no.:	Technical report (U.S. Army Engineer Waterways Experiment Station) ; H-77-8.
Description:	Technical Report Abstract: Tests were conducted to determine the range of gate openings and hydraulic conditions at which the service gates at Big Bend, Stockton, and Clarence Cannon powerhouses can be used for watering-up the scroll case area. The test data should also be applicable to Harry S. Truman powerhouse. Measurements of gate catapult heights, uplift forces, discharge coefficients, and pressures throughout the system were made for various gate openings and pool elevations. Although the model gate was suspended from a wire cable, cable stretch and tension were not simulated. Also, roller bearing and seal friction were somewhat greater in the model than in the prototype. Therefore, some caution should be exercised in application of the data to prototype simulations. For example, if any movement of the gate, however small , occurred in the model it should be assumed that the prototype gate will catapult; operation with these conditions should be avoided. The discharge coefficients that were measured for flow underneath the gate were about as expected. However, the discharge coefficients for the back-of-gate orifices were considerably higher than had been expected. The back-of-gate orifice is actually a submerged, vertical short tube. There is not a plentiful supply of data concerning discharge coefficients for a vertical orifice, but the limited amount of information that is available indicates that the coefficients determined in this study are not unreasonable. The pressures measured at various locations in the penstock, on the gate, and in the scroll case area were not indicative of a blow due to water hammer, although there was a pronounced change in pressures at the time when the scroll case became full and flow started up the gate slot. The pressures measured underneath the gate on the bottom structural member could not be directly related to the uplift force. Although the data could not be generalized for specific design criteria, the following conclusions can be used as guidance for design of intake gates: (1.) If the combined back-of-gate orifice area is greater than the area of the gate opening, the gate will not catapult. (2.) Placing a skin plate on the back of the gate has little effect on uplift forces. (3.) The length of the approach penstock, within the limits tested, has no effect on uplift forces. (4.) The configuration of the area downstream from the gate has an effect on the uplift force. When the gate piers and wicket gate restrict flow there is less tendency for catapult. Thus, the intake gate with the greatest restrictions should be used for watering-up. It is possible that a long downstream penstock would cause greater uplift forces, but this was not proved in this study. (5.) A back-of-gate orifice configuration like that designed for Clarence Cannon powerhouse is very beneficial in reduction of uplift forces with the small gate opening required for watering-up.
Rights:	Approved for public release; distribution is unlimited.
URI:	http://hdl.handle.net/11681/13301
Appears in Collections:	Technical Report