This paper reports an optimization study to characterize the active surface (surface responsible for the radiation capabilities of the device, i.e., the generation of waves) of an axisymmetric heaving point absorber wave energy converter (WEC). For this purpose several hypothesis were considered. Firstly, it was assumed the condition for maximum energy absorption with an axisymmetric point absorber. Additionally, a condition to maximize the device radiation capabilities, which consists of the definition of an active surface depth close to the amplitude of the vertical displacement, was also assumed. Following, a final assumption based on a neglectable near body radiation potential at large distances from the wave generator was also taken into account. Finally, based on all the previous assumptions, it was possible to characterize the WEC active surface through an expression that relates the non-dimensional active surface radius and depth with the relative excursion of the device. This expression allows to understand promptly the size of an axisymmetric heaving point absorber required to optimize the energy absorption according to the most relevant local wave climate.
To support some hypothesis and simplifications (based on the physical phenomenon) taken into account in this work, a BEM numerical code (AQUADYN) was applied for additional confirmation . The code is a three-dimensional radiation-diffraction panel model based on the classic linear water wave theory and potential flow.