1486 / 2024-09-27 18:29:10

Numerical study on the oxygenation effect of deflector-type artificial downflow device

deflector device;,oxygenation effect;,artificial downflow

Variable solutions have been proposed by engineers to mitigate the problem of offshore hypoxia , which is mainly caused by the excessive nutrient load and weak ventilation below pycnocline and also related to the effect of global warming. A recent one is the deflector-type artificial downdraft device. Downflow could be generated along the inclined plate deflector surface, driven by the kinetic energy stored in tidal currents. In this paper, based on the monitored data in the summer of 2020 at Yutai marine ranch in Weihai, numerical experiments are carried out to study the effect of the deflector-type artificial downflow device. Characteristics including the range of the generated downflow, the size of the oxygenation region, as well as the resistance force, are analyzed under different conditions of incoming flow speed and inclination angle of the plate deflector. Results show that a downwelling flow and oxygenation region are generated by the device, enhancing the mixing degree of the water body along the vertical direction. It is also found that the oxygenation effect has a strong correlation with the flow velocity and the inclination angle of the deflector, and is more affected by the former. The stability of the device is also affected by them. Through a comprehensive evaluation of the results with an entropy method, it is found that the device performs best with an inclination angle of 30 ° for flow velocities above 0.3m/s, in terms of the oxygenation effect and the stability of the device. While for incoming velocities below 0.3m/s, the device performs best with the inclination angle of 60°. The performance of deflector matrix with different layout is also investigated. Results in this study provide important references for the engineering application of the deflector device.