Chang, P.-S.; Cho, Y.J., and Hong, C.-B., 2023. Hydraulic characteristics of a forced harmonic oscillator constituting the flap-type wave energy converter: A numerical study using dynamic mesh method (Arbitrary Mesh Interface). In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 558-562. Charlotte (North Carolina), ISSN 0749-0208.

In an effort to develop the WEC (Wave Energy Converter) optimized for Korean marine environment, which is structurally different from those in Europe and the United States, we carried out numerical simulation to look into the power generation efficiency of a forced harmonic oscillator constituting the flap-type WEC. The numerical simulations were conducted using the OlaFlow toolbox, which is based on OpenFoam. In doing so, for numerical simulation of great accuracy, the interaction between the flap-type WEC and incoming waves was described using SixDoFSolidBodyMotion solver and dynamic mesh method such as Morphing Mesh and AMI (Arbitrary Mesh Interface), where computational mesh is adjusted fittingly whenever a forced harmonic oscillator undergoes rotational motion. Numerical results indicate that the oscillator's mass is a key design factor that determines the power generation efficiency of the WEC. If an oscillator is heavier than a critical value, rotational motion of oscillator is centered on the second quadrant, and if an oscillator is lighter than a critical value, its motion is centered on the first quadrant, leading to more efficient harvest of wave energy. The maximum rotational displacement of the oscillator in the shoreward direction occurred after the wave crest passed it, with a time lag due to the oscillator's inertia. In contrast, the maximum displacement in the offshore direction occurred before the arrival of the wave crest. Surprisingly, the maximum force of the wave in the shoreward direction was observed in relatively short waves, rather than in long waves, which was unexpected. These results can be ascribed to the fact that when incoming waves are relatively long, a forced harmonic oscillator is deeply laid down due to larger wave force acting on it. Additionally, when the incoming waves are relatively long, the offshore-directed reflected waves from the forced harmonic oscillator appear to contribute to the effect as well. The numerical results also indicate that the wave force caused by fluid viscosity represents approximately 0.1% of the total wave force. As expected, the longer the incoming waves, the greater the moment acting on the hinge of the WEC becomes.