# Hydrodynamic Investigation on a Land-Fixed OWC Wave Energy Device under Irregular Waves
## 1 Introduction  
With the rapid development of industry and environmental problems caused by the overexploitation of limited fossil fuels resources, the adoption of green and safe renewable energy technologies is now crucial to meet increasing global energy demands. In this regard, ocean energy resources, especially wave energy, have attracted significant attention due to a number of advantages [1]. The average energy density of wind farms is approximately 0.4-0.6 kW/m\({}^{2}\) and solar parks is 0.1-0.2 kW/m\({}^{2}\)[2]. Wave farm energy density is significantly higher at approximately 2-3 kW/m\({}^{2}\). In addition, wave farms can efficiently operate for longer durations, functioning up to about 90% of the time, which is higher than wind farms and solar parks that are affected by the weather and usually generate power 20-30% of the time [2]. These factors demonstrate that wave power is suitable to provide a stable energy supply to the market. Wave energy presents lower negative environmental impacts [3, 4], and is regarded as one of the most promising future renewable energy sources. In the recent decades, a large amount of research has been carried out on wave energy devices and thousands of wave energy patents have been issued [5, 6]. The oscillating water column (OWC) device is one of the most effective technologies in the range of various wave energy converter (WEC) concepts because of its geometric and mechanical simplicities [7]. A number of reviews have been published on the design, working principles, modeling, and optimization of WECs, see for example, [PERSON] [8], [PERSON] [5], and [PERSON] et al. [9]. Somereview studies specific to OWC-WECs have been conducted by [PERSON] [10], [PERSON] and [PERSON] [11], and [PERSON] et al. [12]. According to the aforementioned reviews, most of the past research works on OWC devices concentrated on the hydrodynamic performance of the device in regular wave conditions, and there have been few studies on OWC-WECs in irregular wave conditions. [PERSON] et al. [13] developed a 1D time-domain model for an OWC-WEC. The air pressure and water elevation inside the chamber for regular and irregular waves were computed and the findings were compared with scaled experimental data. [PERSON] and [PERSON] [14] developed a 2D fully nonlinear idealized numerical wave flume (NWF) to investigate wave interaction with a land-based OWC device using a lower-order boundary element method. The hydrodynamic performance of the WEC, and the available power, computed using the time series of the chamber free surface elevation at the chamber midpoint together with the chamber pressures, was studied in irregular wave conditions. However, the chamber-duct area ratio (46.6%) was too large to effectively study the pneumatic effect within the chamber. [PERSON] et al. [15] performed scaled model experiments to examine the hydrodynamic performance of four different OWC models in regular and irregular wave conditions. The relevant integral formula was introduced to calculate the hydrodynamic efficiency in this study. Later, they investigated the hydrodynamic characteristics of the OWC-WECs with a stepped seabed in regular and irregular wave conditions using the open-source code OpenFOAM [16]. Validation of their model was achieved by comparing the experiment data with the numerical results (wave surface spectrum and pressure spectrum inside the central chamber) in irregular wave conditions. The effect of turbine damping and wave conditions on the hydrodynamic performance of an OWC device was evaluated in both regular and random waves by [PERSON] et al. [17]. They found that the influence of the wave height was less significant when compared with the wave period and turbine damping. [PERSON] et al. [18] conducted a model scale test to analyze the operation of OWCs in regular, polychromatic and irregular waves by employing PIV (Particle image velocimetry) technology. [PERSON] et al. [19] performed a number wave-flume tests on a model-scale OWC chamber-turbine system in irregular wave conditions.