An experimental investigation into the constant velocity water entry of wedge-shaped sections

Constant velocity water entry is important in understanding planing and slamming of marine vessels. A test rig has been developed that drives a wedge section with end plates down guides to enter the water vertically at near constant velocity. Entry force and velocity are measured. Analysis of the test data shows that the wetting factor is about 1.6 at low deadrise angles and reduces nearly linearly to 1.3 at 45° deadrise angle. The added mass increases quadratically with immersed depth until the chines become wetted. It then continues to increase at a reducing rate, reaching a maximum value between 20% and 80% greater than at chine immersion. The flow momentum drag coefficient is estimated from the results to be 0.78 at 5° deadrise angle reducing to 0.41 at 45° deadrise angles. Constant velocity exit tests show that the momentum of the added mass is expended in driving the water above the surface level and that exit forces are low and equivalent to a drag coefficient of about 1.0–1.3. Considerable dynamic noise limits the accuracy of the results, particularly after chine immersion.