Experimental study and boundary element method prediction of wave forces on large fixed submerged structures

Wave forces on large fixed submerged structures were investigated in this study. There were two major objectives: the first was to develop an experimental apparatus to measure wave exciting forces on models in a two-dimensional wave tank, and the second was to develop a general boundary element numerical model for predicting the wave forces on structures. Both circular cylinder and rectangular box models were studied in the wave tank. The model depths were adjusted between near the channel bottom, mid depth, and the water surface. Horizontal wave force data were measured under linear waves and random seas. The model significant wave height was approximately 2 cm, and the corresponding wave periods varied from 0.5 to 1.0 seconds. This is equivalent to having the dimensionless wave number (ka) vary from 0.5 to 2.0. A two-dimensional and a three-dimensional boundary element model, based upon constant elements, were developed and validated using experimental data and other numerical solutions. This method has advantages in that the formulation of problems is relatively straight forward and less effort for data preparation is required.;The numerical models were compared with the solutions of a submerged rectangular barge at different water depths. The results showed good agreement and the maximum difference was approximately 4%. Comparison with results from a finite element method applied to a tower-tank structure was within 2%. Further comparison with other numerical methods for different shapes also showed similar good agreement. The comparison of experimental measured data and numerical prediction shows general agreement in the range of wave periods tested, except for the case of the box model located close to water surface where wave breaking was observed.