NUMERICAL SIMULATION OF LONG WAVES (TSUNAMI) FORCES ON CAISSON BREAKWATERS

In this research, long wave (tsunami) forces on caisson breakwaters have been investigated using numerical modeling. Verications of the simulation results using experimental data, analytical formula and empirical formula show that numerical model is capable of modeling the aforesaid problem with enough accuracy. Several numerical simulations have been performed in the framework of this thesis to study dierent parameters aecting the forces induced by long waves on caisson breakwaters. An empirical equation has been introduced to estimate non-breaking long wave forces on caisson breakwaters. Results indicate that the force is a function of water depth and wave period in addition to wave amplitude. By moving the breakwater towards the shoreline, rst, the force decreases, then, the force increases, by changing the shape of the wave, and, nally, the force signicantly decreases after wave breaking. Results suggest that the wave action time on the breakwater shortens by decreasing water depth. Results show that the amount of exerted force by long wave, in our investigated model, is around 3.5 times more than the amount of force by short wave. Moreover, vertical distribution of long wave forces on the structure is more uniform than that for short waves. By increasing the seabed slope, wave amplitude and speed of horizontal orbitals in the wave crest signicantly increase, which further increases wave forces on the structure. Results show that in a sloping bed, by increasing water depth, the eect of changes in bed slope on the amount of wave force is insignicant. Therefore, for relatively deep water, the seabed slope can be overlooked and then the force can be calculated using the formula for at seabeds. The results also show that unlike the previous formula, the pressure unbreaking waves at the still water level is also in uenced by water depth. Based on our results, breaking waves exert forces up to six times more compared to non-breaking waves.