Irregular wave interaction with an offshore OWC wave energy converter

Oscillating Water Column (OWC) with its mechanism based on converting hydrodynamic energy into pneumatic energy is one of the earliest wave energy converters studied by researchers. While the focus of the previous studies were mainly on hydrodynamic efficiency, this paper addresses free surface fluctuation inside the OWC chamber emphasizing on sloshing phenomenon through irregular wave impingement. As reflection response of an offshore OWC plays an important role in energy conversion chain, this paper also provides an insight of wave reflection by such devices. The experimental results show that decreasing damping effect boosts the sloshing energy stored inside the OWC chamber but the ratio of sloshing energy content to the total stored energy inside the chamber decreases; accentuating the importance of tuning short period waves with larger slot sizes. In the context of reflection response of an OWC, relative depth (kd) is the most important factor which can make a great difference in reflection coefficients even up to 100%. Spectral reflection analysis shows that regardless of incident wave height, slot size and draft value, there is a range of relative chamber length (l/L); 0.1 < l/L < 0.30, where spectral reflection coefficient is zero. The only parameter may change the range is incident wave period.