Water Jets as a Draghead Enhancement Device. Hydraulic Model Investigation
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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This report describes the test facility and conditions tested and presents results from a series of laboratory tests conducted to determine the effects of injecting water under pressure using off-the-shelf water nozzles and shop-fabricated water jets in combination with bimetal type agricultural knives to improve dredging quantities in fine compacted sand. The study was divided into two separate tasks. Task A defined the dislodging effects of off-the shelf nozzles having inside diameters of 0.75 and 1.0 in. Task A tests were conducted with the nozzles located at an angle of 30 or 45 deg to the bed, and 1.0 or 4.0 in. above the bed, and water pressures at the nozzle head of 20, 30, 40, or 70 psi. Task B tests involved shop-fabricated water jets and bimetal type agricultural knives in combination with a sectional draghead model. Task B tests were conducted with water pressures of 20, 30, 40, or 70 psi at the water jet, with the water jet positioned either straight or tilted. These tests showed that dredging quantities would increase as a result of installing water jets and knives on dragheads when dredging in fine compacted sand. The results of the laboratory tests were analyzed from an energy efficiency standpoint to provide basic guidance future prototype applications. Even though lower pressure water jets are more energy efficient, the high cost of dredge operation where long haul distances are required may warrant the use of the most erosion-producing device regardless of initial cost or operating cost.
- Civil Engineering
- Fluid Mechanics