Experimental Investigations on the Wall-attached Bubble Growth Process in Water With Supersaturated Total Dissolved Gas

Due to dam discharge, waterfalls, sudden increases in water temperature and oxygen production by photosynthesis, the total dissolved gas (TDG) in water is often supersaturated, which may have serious effects on aquatic ecology. When the atmospheric pressure is lower than the TDG pressure in water, the supersaturated dissolved gas in water will slowly release into air. Wall-attached bubbles were formed during the TDG release process. The generation and departure of wall-attached bubbles influence the release process of TDG in water. To simulate the growth period of the wall-attached bubbles under different pressures, a decompression experimental device was designed to record the supersaturated TDG release process. Based on experimental data and mathematical calculations, the quantitative relationship between the bubble growth rate and environmental pressure was obtained. The supersaturated TDG dissipation rate increases monotonically with increasing relative vacuum degree. Based on the wall-attached bubble growth rate calculation method applied in this paper, a formula of the supersaturated TDG adsorption flux based on wall-attached bubbles was proposed, and a prediction method of the TDG release coefficient was established. The simulation results show that with increasing relative vacuum degree, the TDG coefficient increases correspondingly, and the adsorption mechanism of vegetation surface area can be obviously promoted under lower environmental pressure. This study provides an important theoretical basis for the accurate calculation of the TDG release process and provides a scientific basis for the accurate prediction of the spatial and temporal distribution of supersaturated TDG under different environmental conditions.