Interference effects on the upstream wave generated by the catamaran moving across a depth change

Abstract

With the development of the offshore wind power industry, there is an urgent need to improve the energy efficiency of the operation and maintenance(O&M) catamaran. When the catamaran accesses the offshore wind farm, the vessel could sail on an uneven bottom. Based on our previous study, the effect of the step bottom on the wave-making resistance and upstream wave had been quantified. However, wave interference plays a major role in the hydrodynamic characteristics of the catamaran hull, thus we extended our programme to calculate the hydrodynamic performance of the demi-hulls at the variable water depth. An upstream tsunami could be initiated by the hydrodynamic interaction between the catamaran and the uneven bottom shown from the simulation results, there is an abrupt change in the unsteady hydrodynamic forces as well. The oscillating amplitude and period of the unsteady forces acting on the catamaran are highly dependent on the separation distance between the demi-hulls and speed. The maximum amplitude of the upstream wave and hydrodynamic forces forecast are implemented after the main dimension parameters of the catamaran are determined in the preliminary design. The present simulation programme can supply the reference for the design evaluation of the O&M catamaran in the future.