Experiment to Examine the Effect of Scale on a Breaking Bow Wave

Abstract : A prismatic wedge was towed in fresh water in the David Taylor Model Basin at the Naval Surface Warfare Center, Carderock Division (NSWCCD), generating a large bow wave. Towing speeds ranged from 0.7 to 4.6 m/s, and drafts ranged from 0.6 to 1.5 m. These conditions correspond to Froude numbers from 0.2 to 1.4, Reynolds numbers from 4.1 xl0(exp 5) to 7.0x10(exp 6) (both based on draft, D) and Weber numbers from 11 to 2800 (based on bow radius, R). In addition to the variations in draft and speed, two different bow geometries were investigated: one with a 20 degree bow entrance angle, 20 degree flare, and sharp leading edge, and one with a 40 degree bow entrance angle, no flare, and rounded leading edge. Measurements of free-surface elevations near the bow were made using a laser imaging technique. High-speed video of the spray generated by the bow wave was also analyzed to yield droplet size and velocity distributions. These measurements provide a useful data set to researchers wishing to validate advanced numerical techniques. Presently, the results are used to investigate scaling issues associated with breaking bow waves.