ABSTRACT

The flow states around a cylinder with an arbitrary sectional shape installed m waves have been analyzed by using the singularity distribution methods Then, the theoretical wave force equations have been newly obtained by applying the above velocity potentials to the momentum equation expanded into unsteady flows. Moreover, inertia coefficient CM and drag coefficient CD in Morison's formula have been estimated by applying the wave forces calculated from the above equations to Morison's formula. As typical examples, the flow states around a circular cylinder have been shown, and wave forces acting on the cylinder have been calculated to obtain the values of CM and CD.

INTRODUCTION

For this reason, it is necessary to establish a theoretical method to analyze the flow states around a cylinder with an arbitrary sectional shape and to estimate the wave forces acting on the cylinder. One of the authors Ishida(Ishida and Tamura,1988) has theoretically analyzed the wave forces acting on a Circular cylinder installed in the wave field to make clear the generation mechanism of drag forces due to wake vortices. This paper further aims at the establishment of theoretical analysis of both flow states around a cylinder with an arbitrary sectional shape in the wave field and the wave forces acting on It From this viewports, the following research have been done:

1. The flow states around the cylinder including the vortex shedding from the separation points to show the wake region have been analyzed by using the two kinds of singularity-distribution methods m which the cylindrical body is approximated by many source densities or many point vortices

2. The wave force equations in both methods have been newly obtained by applying the complex velocity potentials to the momentum equation expanded into an unsteady flow.

3. Inertia coefficient CM and drag coefficient CD in Monson's formula have been estimated by applying the wave forces calculated from the above wave forces equations to Monson's formula.

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