Semi-empirical Formulas Of Drag/lift Coefficients For High Speed Rigid Body Manoeuvring In Water Column
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163 - 172
P. C. Chu, C. Fan & P. R. Gefken
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
body-flow interaction, bomb manoeuvring, body trajectory and orientation, drag/lift coefficients, inverse modeling, bomb drop experiments.