Experiments on the water entry of curved wedges: High speed imaging and particle image velocimetry

In this work, we experimentally study the water entry of curved rigid wedges. Experiments are performed on two groups of rigid wedges comprising five specimens each. Each group has a fixed mean deadrise angle (25 degrees and 35 degrees) and varying radius of curvature. Drop tests are conducted in free-fall, and the drop height is parametrically varied to investigate the effect of the entry velocity on the pile-up evolution, the impact dynamics, and the energy transferred to the fluid. Specifically, high speed imaging is utilized to simultaneously measure the penetration depth of the wedge and its wetted surface. Experimental results are used to compute the pile-up coefficient, which is found to be largely independent of both the wedge geometry and the entry velocity, while exhibiting modest variations as a function of the penetration depth. In addition, particle image velocimetry is used to investigate the flow physics generated by the water entry, and especially dissect the energy absorbed by the risen water during impact. Results show that between 60 and 80% of the impact energy is consistently transferred to the risen water, which accounts for the formation of the pile-up and the spray jets. (C) 2014 Elsevier Ltd. All rights reserved.