Experimental investigation of water entry of a solid object and sand particles

Abstract

This thesis presents the results of two different approaches to water entry; first, in Part I, the results of the experimental investigation of the water entry of a solid object, a thick disk in stagnant water, are presented. The shape of the resulting surface crown in different release conditions and disks with various geometries should be characterized. Moreover, the pinch-off time and depth of the underwater cavity for disks with different densities in different release conditions are extracted and results are compared in different conditions. Energy losses due to the impact are also obtained and the results for different release heights and various disk densities are presented. A parameter study reveals the dependence of the underwater cavity structure on the governing dimensionless groups. The results of annular disks are also illustrated to see how a central hole can affect the pinch-off characteristics. In addition, the effects of confinement on the characteristics of the crown, pinch-off time, and pinch-off depth are investigated and results are compared with the condition of removing wall effects. The wall effects highly reduced the radial and vertical velocity of the surrounding water. Less vorticity with asymmetrical distribution is observed in the surrounding water. Consequently, less swirling strength, and mean and turbulent kinetic energies are observed in tanks with smaller widths. [...]