Author(s)

M. Rahman & S. H. Mousavizadegan

Abstract

This paper deals with an elliptical cylinder in regular waves and investigation is made to determine the exciting forces and moments exerted on this body in regular waves. We have used the potential theory formulation in this case under the assumption that the viscous effects are negligible. An analytical solution to the linear wave diffraction problem, in terms of the infinite series of Mathieu’s function, for a fixed vertical cylinder of elliptical cross-section in water of finite depth d has been presented. Further, Mathieu functions were simplified by taking the characteristic number s to be independent of the parameter q. The values of these simplified forms of Mathieu functions are substituted in the closed form approximations for the force and moment components for small eccentricity e of the cylinder, and the results thus obtained are compared with the existing results in the previous literature. The comparison shows good agreement except for e = 0.9 and e = 1.0. The limiting case of the circular cylinder, obtained by taking e = 0, has also been studied. The horizontal and vertical forces for the circular and elliptical cylinder for angle of incidence α = 0◦ and 90◦ have been compared. Keywords: hydrodynamics, loading, forces and moments, elliptic cylinders, regular waves, finite depth oceans, diffraction, scattering. 1 Introduction The determination of wave forces on offshore structures is essential to study the effects of waves, wind and current on them. The offshore structures should experience minimal movement to provide a stable work station for operations such as drilling and production of oil. The solution to the problem of ocean wave interaction with offshore structures is usually very complex. In many cases, only

Keywords

hydrodynamics, loading, forces and moments, elliptic cylinders, regular waves, finite depth oceans, diffraction, scattering