Author(s)

S. Chakrabarti & A. Gupta

Abstract

The steady wave drift force on a submerged body is a second-order quantity. With a potential flow assumption, the force arises from the diffraction and radiation of the waves from the interaction with the body. For a fixed body in waves the steady force is contributed from the wave diffraction effect alone. Numerical solutions are generally needed for the computation of the steady drift force on submerged structures. In this paper the steady wave drift forces on several fixed bodies of basic shapes are derived in closed form. The paper addresses the steady drift forces on the following basic structures: a vertical circular cylinder, a submerged horizontal cylinder, a bottom-seated horizontal half cylinder, and a bottom-seated hemisphere. The results developed demonstrate the importance of various independent non-dimensional parameters. A numerical program based on linear diffraction/radiation theory is used to validate the closed form solution. Keywords: basic objects of symmetry, closed form solution, design curves, steady drift force, wave structure interaction. 1 Introduction The linear wave forces on a large structure are computed from the linear diffraction theory based on the (Bernoulli’s) linear pressure term in its equilibrium position up to the still water level. However, the structure motion, wave free surface, and the (Bernoulli’s) nonlinear pressure terms introduce nonlinear forces on the structure not predictable by the linear theory. The steady wave drift force has been shown to derive from the first order wave potential. The 3-D diffraction/radiation theory is well established to compute these forces.

Keywords

basic objects of symmetry, closed form solution, design curves, steady drift force, wave structure interaction.