Hydraulic Studies of a Sudden Enlargement Energy Dissipator Used Downstream from a Gate Valve

摘要

Limited studies were made under high heads to determine the effectiveness of a sudden enlargement type energy dissipator used downstream from an 8-inch gate valve. The enlarged section, which started at the downstream flange of the valve, was 16 inches in diameter (2.0 D1) and 80 inches long (5.0 D2). The valve throttled at heads up to 600 feet. Discharges of 1.0, 3.0, and 5.0 cfs were tested. A back pressure, or downstream depth of water, of only 1.0 foot above the centerline of the 16-inch pipe was sufficient to maintain the enlarged pipe full and obtain satisfactory energy dissipation at all conditions tested. The water surface in the open tank just downstream from the enlargement was rough when the depth above the pipe centerline was small, but became much smoother at depths of 5 and 6 feet. Cavitation ranged from moderate to severe within the enlarged pipe. Admission of air at the extreme upstream end of the enlargement greatly reduced cavitation noise and vibration. (Author)