Inverse problem of Morison equation for a perforated-ball velocity meter: an improved method

A Perforated-ball Velocity Meter (PVM) device measures the wave induced for ces on a cantilevered ball-tube assembly and the wave kinematics is compute d from these forces by solution of an inverse problem given by the Morison' s equation. The drag and inertia coefficients of both the ball and the tube are experimentally determined and the forces on both the ball and the tube are used in the inverse Morison problem. The behaviour and convergence of the numerical scheme for this inverse problem has been studied in detail. T he laboratory experiments conducted using the PVM and the measured kinemati cs have been compared with calculated kinematics obtained from the free sur face elevation measurements using the linear wave theory and the Wheeler st retching theory. The comparisons have been satisfactory. It is also shown t hat the kinematics measured by the PVM can yield the free surface elevation with good accuracy. (C) 2000 Elsevier Science Ltd. All rights reserved.