NONLINEAR HYDRODYNAMIC FORCES ACTING ON CYLINDERS HEAVING ON THE SURFACE OF A FLUID

Abstract

1. Introduction / 2. Model Experiments / 3. Analysis of the experimental results and comparison with the theoretical result / 4. Viscous effect on N_z / 5. ConclusionLinear and nonlinear hydrodynamic forces are investigated by using two-dimensional cylinders heaving with large amplitude on a free surface. Sections of the cylinders are circle, Lewis form, bulbous bow form (deep and shallow draft) and triangle. The hydrodynamic forces acting on the cylinders and the concurrent progressive wave heights are measured. First, second and third order forces are obtained from the measured forces by using Fourier analysis. The first order forces and wave heights are compared with values calculated by linear theory. The second-order forces of the circular cylinder are compared with the values calculated by Lee, Parissis and Potash using perturbation method. Also, the influence of viscous drag force upon the damping coefficient is discussed