## 4 Conclusions  
In this study, a hydraulic model experiment was conducted to investigate the behavior and power generation characteristics of a bottom-hinged flap-type WEC with an inversed triangular prism shape and a rotary generator in the presence of a reflection wall, assuming breakwaters behind the WEC in unidirectional regular waves. The behavior of the flap depending on the water depth \(h\), wave steepness \(H_{i}/L\), and distance from the reflecting wall \(D\) can be classified into patterns A and B that can generate power stably, pattern C that is unstable but that can generate power, and patterns D and E that cannot generate power. The effect of the position from the reflection wall is dominant on the flap pattern, and the flap tends to be unstable as the ratio of the wavelength and the distance from the reflection wall to the flap, i.e., \(D/L\), approaches 0.5, which is the anti-node position of the standing wave. Moreover, when the water depth is greater than the flap height, the flap tends to be unstable. Therefore, the installation location of the bottom-hinged WEC with a reflection wall should avoid the condition \(D/L\approx 0.5\), and if the wave power of the installation location is relatively small, it is suggested that the flap height should be greater than the water depth for stable power generation. As a result of  
Figure 21: Screenshots of the flap motions for the case of \(D=1.09\) m, \(h=0.525\) m, \(T=2.2\) s, and \(H_{i}=0.12\) m at (**a**) \(t/T=1/8\) to (**h**) 8/8. \(D/L\) is 0.2355 and \(k_{e}=0.18\). The blue arrow denotes the wave direction acting on the flap, and the white dotted line indicates the rotational neutral axis of the flap. The blue solid line denotes the water surface. Figure 20: Screenshots of the flap motions for the case of \(D=1.45\) m, \(h=0.425\) m, \(T=2.6\) s, and \(H_{i}=0.12\) m at (**a**) \(t/T=1/8\) to (**h**) 8/8. \(D/L\) is 0.2852 and \(k_{e}=0.44\). The blue arrow denotes the wave direction acting on the flap, and the white dotted line indicates the rotational neutral axis of the flap. The blue solid line denotes the water surface. the power generation characteristics in pattern A that can generate power stably, it was demonstrated that the wave power capturing ability of the wave power generation system used in the experiment is 30%, and the maximum power generation efficiency \(k_{e}\) is 0.77 at \(D/L\approx 0.32\). Theoretically, it is well known that the maximum \(k_{e}\) can be obtained at \(D/L=0.25\), which is the node of the standing wave formed by the reflection wall. However, the position of \(D/L\) at which the maximum \(k_{e}\) appears can be changed by the effects of the flap shape on the flow fields around the flap and the resistance of the PTO system on the phase difference between the reciprocating behavior of the flap and the period of the standing wave. Based on the relationship between \(k_{e}\) and the characteristics of the flap motion, the flap tends to be temporary latching on the offshore or shore side during the pitching motion, and the rotational center of the flap is tilted to one side depending on \(D/L\) and \(h\). These phenomena contribute to the reduction of the wave power capturing ability such that it is considered that the maximum \(k_{e}\) appears at D/L \(\approx 0.32\), where there is no latching effect and there is a lesser tendency of tilting of the rotational center of the flap. As the effects of the damping PTO system and the flap shape on the flap motion during rotation were not clarified in this study, further research is required to consider these types of effects on power generation performance. Conceptualization, Y.-H.C. and N.M.; Methodology, T.N. ; Formal Analysis, Y.-H.C.; Investigation, K.-H.L. ; Writing--original draft preparation, K.-H.L. and Y.-H.C.; Writing--review and editing K.-H.L. and Y.-H.C. All authors have read and agreed to the final manuscript. The publication of this article was funded by the research support project of Catholic Kwandong University.