The Wave Focusing Effect of a Parabolic Wall

The energy generation efficiency of a wave energy conversion system is in general proportional to the capacity of wave energy capture of the system. In various wave energy conversion systems, a configuration with parabolic shape has shown advantages in wave capture dynamics. This paper presents an experimental investigation into the wave focusing and elevation in a parabolic wall area with a Laser Wave Height Measurement equipment named as IVP Ranger SC386. In the experiment, the tested waves were described by a dimensionless factor WF which consists of wave parameters and the parabolic wall size. The WF increases with wave relative size to the model. The tested wave obliquities to the parabolic wall were 10 and 20 degrees in addition to the normal incident waves. A tube with an inner diameter 7.5cm, representing a chamber for oscillatory water columns compressing air, was mounted at the focus area. The elevations of wave height inside the tube with a sealed and an open top, as two different cases, were also measured. Furthermore the wave forces acting on the parabolic wall were measured using load cells. The analysis of the experimental results revealed that the parabolic wall was able to significantly elevate wave heights by up to 2.5 times. Within 10 degrees the wave obliquity effect can be neglected for both forces acting on the parabolic wall and wave height elevated by the parabolic wall. A prediction equation for focusing wave height was developed from the experimental results and the parabolic focusing principle.