Numerical Study of Conventional Oscillating Water Column and Oscillating Water Column Using Helmholtz Resonator on Non-Linear Wave Input with Sloshing Characteristics

Abstract One of the latest OWC concepts that is expected to improve OWC performance and lessen the sloshing phenomenon is the Helmholtz resonator OWC. This study uses the Reynold Averaged Navier-Stokes (RANS) based CFD method with the k-ω SST turbulence model. 2D modeling is performed under transient conditions by applying the Volume of Fluid (VoF) technique to model the sloshing phenomenon in the OWC. According to the simulation result on input waves with sloshing characteristics (T = 1.08 s, H = 0.13 m, H/L = 0.073) the Helmholtz resonator OWC ( S c = 0.05 m, e = 0.01 m, e = 0.05 m) produces better performance with ξ by 17%, C r by 7% and is able to prevent energy loss ( C d ) up to 9.4% compared to the conventional OWC ( S c = 0.05 m, e = 0.05 m, e = 0.01 m). From the results of the OWC airspace velocity contours, it is found that the conventional OWC has a larger and faster vortex shedding than the Helmholtz resonator OWC. In this case, the Helmholtz resonator OWC in waves with sloshing characteristics can reduce the effect of turbulence-shedding vortex caused by waves with sloshing characteristics much better than the OWC.