Author(s)

P. C. Chu, C. Fan & P. R. Gefken

Abstract

Falling of rigid body through water column with high speed is investigated experimentally and theoretically. Several experiments were conducted to shoot rigid bodies with the density ratio higher than 1 into the hydrographical tank. During the experiments, we carefully observe the position and orientation of the bomb-like rigid bodies. Using the experimental data a semi-empirical formulas for the drag/lift coefficients were obtained. With the given drag/lift coefficients, the momentum and moment of momentum equations of a fast-moving rigid body can be integrated numerically. The numerical results are well compared by the experimental data. Keywords: body-flow interaction, bomb manoeuvring, body trajectory and orientation, drag/lift coefficients, inverse modeling, bomb drop experiments. 1 Introduction Study on falling rigid body through water column with high water entry speed has wide scientific significance and technical application. Scientific studies involve nonlinear dynamics, body and multi-phase fluid interaction, supercavitation, bubble dynamics, and instability theory. Technical application of the hydrodynamics of a rigid body moving fast in fluids includes aeronautics, navigation, and civil engineering. The rigid-body dynamics allows one to set up six nonlinear equations for the most general motion (Chu et al., 2004, 2005a, b): three momentum equations and

Keywords

body-flow interaction, bomb manoeuvring, body trajectory and orientation, drag/lift coefficients, inverse modeling, bomb drop experiments.