Laboratory Investigation on Hydrodynamic Performance of an Innovative Aeration Device with a Wave-Driven Heaving Buoy

Abstract

Coastal seawater quality is of significance for the environment, ecology and fisheries. In recent years, the hypoxia or anoxia problems of bottom seawater aggravated due mainly to the seawater stratification and eutrophication. This paper addresses an innovative aeration device with a wave-driven heaving buoy to enhance the dissolved oxygen concentration for bottom water. A series of physical experiments was conducted to investigate its hydrodynamic performance and air flow rate. The response amplitude of heaving components and the average value of air flow rate were examined with the related parameters, including incident wave height, incident wave steepness and aeration depth. It was found that with increasing incident wave height, the average heaving displacement and the average air flow rate increase respectively. With the increase of incident wave steepness, the relative value of average heaving displacement increases obviously for high wave period scenarios, it increases slightly for small wave period scenarios in comparison and the relative value of air flow rate increases evidently. With the increase of aeration depth, the average heaving displacement and the average air flow rate decrease respectively. With the increase of relative aeration depth, the relative value of average heaving displacement and the relative value of air flow rate decrease respectively. In addition, the dimensional analysis and the least squares methods were used to obtain the prediction formulas for the average heaving displacement and the average air flow rate, and they agreed well with the related experimental data.

Temporal and Spatial Analysis of Coastal Water Quality to Support Application of Whiteleg Shrimp Litopenaeus vannamei Intensive Pond Technology

“…The low concentration of dissolved oxygen in the dry season measured in August and September can also be caused by low sea waves. Waves or ocean waves increase dissolved oxygen [87,88], so low waves in August and September also impact low dissolved oxygen concentrations. September, October, and November are the lowest sea waves in the Flores Sea [89].…”

Temporal and Spatial Analysis of Coastal Water Quality to Support Application of Witheleg Shrimp, <em>Litopenaeus vannamei</em> Intensive Pond Technology

“…The low concentration of dissolved oxygen in the dry season measured in September can also be caused by low sea waves at that time. Waves or ocean waves tend to increase dissolved oxygen [119,120], so low waves in September also impact low dissolved oxygen concentrations. September, October, and November are the lowest sea waves in the Flores Sea [121].…”

“…Meanwhile, dissolved oxygen in water can be reduced due to respiration and decomposition of organic matter on the bottom of the water [137,138], causing a decrease in dissolved oxygen in water, where a decrease in dissolved oxygen concentration to a critical point will cause hypoxia. Hypoxia (dissolved oxygen concentration < 2.0 mg/L or about 30% saturation) is a phenomenon that occurs in the aquatic environment due to a decrease in dissolved oxygen concentration to a limit that can contribute greatly to a decrease in the growth and reproduction ability of aquatic organisms and even death of aquatic organisms in the water [132,139,140]. Nitrate is a form of N that is less toxic than nitrite and ammonia, but it can be toxic to shrimp at high concentrations.…”