Nonlinear Wave Forces on Vertical Cylinder

The method of diffraction is applied to Stokes’ fifth order gravity wave theory to obtain an expression for the velocity potential in the cylindrical polar coordinate system. Based on this expression, the dynamic pressure at the surface of a vertical cylinder and the total horizontal force on the cylinder in the direction of the wave propagation are determined. The wave force is written in an equivalent form of the inertial part of Morison’s equation and the effective inertial coefficients are shown to be functions of a single dimensionless quantity. The different parameters involved are plotted or tabulated so that forces on a vertical cylinder due to a nonlinear wave up to fifth order may be easily evaluated. Correlation of the theory with the available experimental data was found to be reasonably good.