Hydrodynamic behavior and oxygen transfer performance of a new device utilizing wave energy to transport surface water to deep ocean zones

Dissolved oxygen (DO) concentration is a significant indicator of marine environment and ecology, and hypoxia occurs frequently in deeper seawater. We present a new wave energy utilization device to transport superficial oxygen-rich water to deeper hypoxic zones. A series of experiments were conducted and a simple 3-D CFD model was developed to investigate the hydrodynamic behavior and oxygen transfer performance of the device for waves. With increases in wave heights or periods, the response amplitude (RA) of heaving components and the average flow rate in inlet tube increased. However, RA decreased when distance between the entrance of inlet tube and the flume bottom increased. For relatively small wave period scenarios, relative RA increased with increasing wave steepness; however, for relatively large wave period scenarios, it increased to a peak and then decreased with increasing wave steepness. With the increase in equivalent damping coefficient or buoy relative height, relative RA of heaving buoy decreased. The oxygen transfer coefficient on the wave surface increased with increasing wave steepness. The DO concentrations and oxygen transfer coefficients were higher in the scenarios with the device than in those without the device, indicating that a high oxygen transfer efficiency could be accomplished using the device.