Effect of Impact Velocity and Mass Ratio during Vertical Sphere Water Entry

Dillon Schwalbach ； Thomas Shepard ； Seamus Kane ； David Siglin ； Teegan Harrington ； John Abraham

《Development and Applications of Oceanic Engineering》 3卷 (2014/11) Pp. 55-62

並列摘要

The cavity formation and drag forces following spherical object impacts on a water free surface have been observed experimentally from the period of initial impact to cavity pinch-off. The impact velocity, sphere density, and surface wettability were varied while the diameter was held near-constant (39.3-39.9 mm). Impact velocity was varied between 2.4 m/s and 6.8 m/s and the sphere density was varied between 656 kg/m^3 and 6760 kg/m^3. Increasing impact velocity while keeping sphere density constant was shown to result in an deeper cavity pinch-off and a decrease in pinch-off time. Increasing sphere density while keeping impact velocity constant results in an increase in cavity pinch-off depth and pinch-off time. A correlation was observed between the ratio of the kinetic energy of the sphere and the surface tension of the water with the dimensionless depth of the cavity pinch-off, independent of surface wettability. The dimensionless time of the cavity pinch-off with respect to gravity was found to be near constant, and independent of sphere density, impact velocity, and surface wettability. The dimensionless time of the cavity pinch-off with respect to impact velocity was found to increase linearly with liquid Weber number.

並列關鍵字

Water Impact Forces ； Underwater Trajectory ； Oceanography ； Expendable Bathythermography ； Water Cavity Formation ； Hydrophilic Surfaces ； Hydrophobic Surfaces