An experimental investigation into the effects of front wall geometry on OWC performance for various levels of applied power take off dampings

Abstract

Despite the achieved progress, exploiting wave energy in a competitive and efficient manner is still a grand challenge problem. This study aims to improve the performance of an Oscillating Water Column (OWC) by experimentally testing different streamlined front wall underlip geometries. Results show that the proposed geometries have an important bearing on OWC hydrodynamic performance provided that OWC does not operate in sloshing mode. Relative to rectangular front wall plate, underlip geometry with a circular cross-section, provided a maximal increase of 21.2% in capture width ratio via reducing vortex shedding and increasing conveyed amount of incident wave energy into the chamber. Observations indicate that the value of Power Take-off (PTO) damping has a crucial impact on the amount of acquired performance improvement. Therefore, applied PTO damping is a key parameter that has to be determined with care. All tested geometries failed to diminish the sloshing present in the chamber which highlights the fact that sloshing phenomenon is only associated with incident wave characteristics independent of wave-structure interaction. Introduced front wall shapes are also found significant from structural design point of view as they are beneficial in attenuating large vortex induced shear stresses that OWC front wall has to endure.