Numerical Investigation of the Characteristics of Crossflow Air Turbine under Irregular Waves for Wave Energy Conversion

Abstract

The global energy crisis and climate change are major worldwide concerns. As a solution, renewable energy sources are gaining attention, with wave energy being underutilized but notably promising due to the extensive coverage of oceans. Among the various wave energy converters (WECs) being developed, the oscillating water column (OWC) is particularly significant due to its relatively simple mechanism, which uses fewer moving parts above the water level. Although the Wells turbine is the most used power take-off (PTO) system for OWCs due to its high peak efficiency, its application is limited due to the aerodynamic stalling effect at higher flow ranges.

Crossflow Air Turbines (CFATs) have emerged as a viable alternative, offering broader operational capabilities and stable efficiency across a wide range of flow coefficients. Recent research (Baddegamage et al., 2025) showed the performance of CFAT with a peak efficiency of 0.71 at flow rate coefficient (Φ) of 0.41 in steady unidirectional flow. Moreover, the CFAT showed a peak efficiency of 0.68 in bidirectional flow at Φ = 0.53. The CFAT ensures stable efficiency over a broad range of flow coefficients, making it more effective for sustaining performance under fluctuating or higher flow conditions. To further understand the behaviour of CFAT under real operating conditions, it is critical to assess the performance of the CFAT in a more accurate representation of ocean conditions in irregular waves. This study aims to investigate the performance numerically using computational fluid dynamics (CFD). The transient numerical model is based on Reynolds-averaged Navier–Stokes equations with SST k-omega turbulence model. The JONSWAP spectrum is used to simulate irregular waves, considering two dominant sea states off the Korean coast. The numerical simulations provide the time histories of key performance parameters such as torque, and total pressure drop across the rotor. Moreover, the effect of significant wave height and the peak period on transient non-dimensional coefficients is investigated. This approach could benefit the advancements in wave energy harvesting using CFAT as a PTO in OWC.