Hydro-Elastic Behavior of an Inflatable Mattress in Waves

The wave induced motion response of an inflatable mattress has been studied by wave basin experiments and numerical simulations. The floater of this study is developed by the Solar@Sea II consortium for the purpose of offshore floating solar. Flexible thin-film PhotoVoltaic panels with small bending stiffness are glued on top of the mattress. The bending of the mattress in waves needs to be understood in order to quantify the fatigue loading on the PV panels. Wave basin tests have been performed for a range of wave lengths in order to identify the floater’s local vertical response and global horizontal response. As expected, the mean wave drift force is close to the theoretical value of a reflecting wall for short waves where the vertical RAO is small. For longer waves, where the vertical motion RAO approaches unity, the drift force reduces rapidly. Numerical simulations have been performed using the linear diffraction software SEACAL developed by CRS (Cooperative Research Ships). The dynamic response is calculated as a superposition of N-orthogonal mode shapes, which are determined in air by the Finite Element Method. In general there is a reasonable agreement between the wave basin experiments and numerical results. The largest discrepancies are on the floater edges, where the simulations predict an amplification which is not seen in the tests. Consequentially, the calculated drift forces are over predicted in the simulations.