A GENERAL-METHOD FOR CALCULATING HYDRODYNAMIC-FORCES

This paper presents the derivation of a general method for calculating wave forces on the cylindrical members of offshore structures. By mea ns of the proposed method one can calculate the wave loading on cylind rical members of fixed or floating offshore structures orientated rand omly in waves. This method of calculating wave forces is based on the linear Airy wave theory. Calculation procedure of wave force component s is presented in great detail on the basis of wave particle kinematic properties obtained from the linear Airy wave theory. In the procedur e of calculating wave forces presented, definitions of the wave refere nce system for propagating wave, the structure reference system for th e platform and the member reference system for the tubular members of the structure are first established, and then the calculation of wave forces is given in terms of its components, which are pressure, accele ration and velocity forces, including current forces. At the end of th e paper, expressions of total heave, sway and surge forces and total r oll, pitch and yaw moments acting on the platform are given as a sum o f these forces acting on each member of the platform. The calculation procedure derived in this paper provides a very efficient means of cal culating wave forces and moments during the time-domain simulations of a floating platform experiencing large amplitude motion in intact, pr ogressive flooding and damaged conditions. Comparisons of the predicti ons with the measurements which will be presented elsewhere reveal tha t the calculation procedure developed can predict large amplitude osci llatory and steady motion characteristics of an intact and damaged pla tform in waves with an acceptable degree of accuracy.