http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
effect of wave-current interactions on the hydrodynamic loading of large offshore structures
xvii, 143 leaves : illustrations ; 29 cm
The influence of wave-current interactions on the fluid loading of large offshore structures has been investigated by extending the conventional diffraction theory approach to include the changes in the incident and scattered wave fields caused by the presence of a steady current. Modifications in the wave height are based upon the principle of conservation of wave action. The waves are assumed to be linear so that the effect of the current on the short-term force spectrum can be determined from the transfer function and modified Pierson-Moskowitz spectrum. A three-dimensional hybrid finite element method for computing wave forces on structures of arbitrary geometry in still water has been extended to consider the case of waves on a current. Validation of this numerical model has been performed by applying the method to a vertical circular cylinder in water of constant depth. An analytical solution for wave and current forces on a cylinder has been developed and compared with the numerical solution. In both cases, the velocity profile of the current is assumed to be uniform with depth and the flow field is uniform at infinity with a dipole at the origin. The results indicate that the dispersion relation for waves on the flow field around the structure is a function of the position coordinates, but reduces to the dispersion relation for waves on still water at the stagnation points of the flow. The maximum changes in incident wave height occur at the cylinder surface where the flow velocity is maximum. The properties of the incident wave field vary with the wave period, current velocity, current direction and position coordinates in the flow field. In the analytical solution, the coefficients of the series solution for the scattered waves become functions of the angular coordinate. For all currents, the free surface elevation at the stagnation points remains equal to its value for waves in still water. However, the total velocity potential at the stagnation points varies with the current strength and direction. The horizontal forces and overturning moments on the structure increase with opposing currents and decrease with following currents.
Ph. D. in Philosophy Texas A & M University 1982
Includes bibliographical references (leaves 113-116).