# Hydrodynamic Investigation on a Land-Fixed OWC Wave Energy Device under Irregular Waves
## 5 Conclusions  
In the present work, the hydrodynamic characteristics of a land-fixed OWC wave energy converter under the action of irregular wave conditions is numerically investigated. Based on potential flow theory, a 2D, fully nonlinear numerical wave flume is established using the time-domain higher-order boundary element method (HOBEM). In the numerical simulations, the inner-source technique and JONSWAP wave spectrum was used to generate the irregular incident wave conditions. The results show that the significant wave heights at the chamber center-pointand the pneumatic pressures in the chamber are lower in irregular waves than those in regular waves over a relatively broad range of wave frequencies. Similarly, the hydrodynamic efficiency in irregular wave conditions is lower than that in regular waves over a relatively broad range of wave frequencies. Figure 14: The comparison of free surface elevation spectra at the chamber interior for G3 and G4. (a) \(k_{p}h=3.010\), (b) \(k_{p}h=2.578\), (c) \(k_{p}h=2.186\), (d) \(k_{p}h=1.700\), (e) \(k_{p}h=1.258\), (f) \(k_{p}h=0.750\). wide frequency range especially at the resonant frequency. In the low-frequency wave conditions, a slightly higher hydrodynamic efficiency is observed for the irregular waves when compared to the regular waves. The maximum instantaneous pneumatic power are approximately 14 times greater than average values. Thus, the stability of the PTO needs to be taken into consideration in the practical applications. The resonant sloshing phenomenon is observed in this model. With the relative peak wavelength (\(\lambda_{p}/\mathrm{B}>2\)) increasing, the sloshing motion in the chamber weakens and the piston motion free surface displacement dominates. The viscous effects which could induce vortex shedding at the front wall and boundary layer shear stresses at the OWC device chamber walls are neglected in the present study. Future studies should consider these effects in order to obtain as more accurate prediction of the fluid structure-interactions, the forces applied to the OWC chamber walls and the free surface displacement. It is suggested that a systematic, fully nonlinear CFD study be undertaken in the future to investigate and quantify these aspects thoroughly. Conceptualization, Z.Z., R.W. and D.N. ; validation, S.K., R.W. and R.M. ; formal analysis, S.K., R.W. and R.M. ; investigation, S.K., R.W., R.M. and D.N. ; writing--original draft preparation, S.K. ; writing--review and editing, Z.Z., S.K., R.W., R.M. and D.N. ; supervision, D.N. ; project administration, D.N. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (Grant No. 52001054), Liaoning Revitalization Talents Program (Grant No. XLYC2002033), Liaoning BaiQian-Wan Talents Program (Grant No. 2020921007), Natural Science Foundation of Liaoning Province (Grant No. 2021-BS-060) and Fundamental Research Funds for the Central Universities (Grant No. DUT21 LAB116). Not applicable. Not applicable. Not applicable. The data presented in this study can be obtained on request from the corresponding author. The authors declare no conflict of interest. * [PERSON] et al. (2017) [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; [PERSON] Experimental investigation of different geometries of fixed oscillating water column devices. _Renew. Energy_**2017**, _104_, 248-258. [CrossRef]
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