Various types of wave energy absorption equipment work based on a swing or a submerged buoy to a fixed reference. The efficiency of this equipment can vary based on the depth of water in which they are installed. One of the equipment that can effectively use both components of wave forces in x and y direction is Bristol cylinder which was first introduced by Evans from the University of Bristol in 1976 [1]. Evans provided a linear theory to predict the performance of this group of wave energy absorption equipment and indicated that, in theory, there is a possibility of 100% absorption for wave energy using the cylinder [1]. He also showed that passing waves can be eliminated and the total wave energy can be absorbed for certain values of the spring constant and damping factor in each frequency of incident wave. Recently, Heikkinen et al. [2], through providing a theoretical analysis based on potential flow theory, investigated the effect of various parameters such as height, wave periodicity, and the cylinder diameter on the cylindrical Bristol efficiency.Evans [3] and Davis [4] experimentally showed that linear theory quite loses its accuracy in calculating the Bristol cylindrical efficiency for waves with high sharpness. This is due to limiting assumptions of linear theory which ignore the effects of viscosity and assumes the non-rotating flow and linear waves.A common method for considering the effects of viscosity in non-viscous fluid simulations is adding a sentence of similar force with the drag force in the well-known Morison's equation [5]. This method has been used by many researchers, including Davis [4] and Babarit et al. [6]. Regarding the Bristol cylinder, Davis [4] showed that the use of this method for predicting efficiency does not provide acceptable results. In fact, because of the cylinder movement, the drag coefficient is different at any given moment and considering a fixed amount for the drag coefficient cannot accurately predict wave forces.Hence, providing a method for predicting the performance of the Bristol cylinder in various conditions, including against irregular non-linear waves, seems essential. In this study, using a method based on the unmatched and fixed networking (fast fictitious domain method), the performance of this wave energy absorbent in different conditions is simulated.

Keywords