RUN-UP ON A STRUCTURE DUE TO 2ND-ORDER WAVES AND A CURRENT IN A NUMERICAL WAVE TANK

A numerical wave tank is considered in which the interaction between w aves, current and a structure is simulated by a 3D boundary element mo del in the time domain. Through a Taylor series expansion and a pertur bation procedure the model is formulated to second order in wave steep ness and to first order in current speed. The boundary-value problem i s separated into a known incident wave field and an unknown scattered wave field, the latter being absorbed at the radiation boundaries usin g active wave absorption. The present paper focuses on the wave run-up on a structure in waves and current. For the simulations a bottom mou nted vertical circular cylinder is chosen. The numerical results show good agreement with previous analytical and numerical solutions for se cond-order wave diffraction without a current and first-order wave dif fraction with a collinear current. The inclusion of a current in the c alculation of second-order wave run-up is new and the validity of the results is demonstrated by a parametric study. It is shown that both t he current and the second-order wave components are of significant imp ortance in calculating magnitude and location of the maximum run-up on a structure. (C) 1998 Elsevier Science Ltd. All rights reserved.