Research on the plume stability of air bubble curtains under low transverse flow velocity environment in dredging engineering

Abstract

Air bubble curtain anti-fouling systems, which meet both the environmental standards of suspended solids diffusion and navigation requirements, have unique advantages in environmental dredging technology. Through the bubble plume formed by dense bubble hole jets, the bubble curtain blocks the material exchange between the designated area and other areas in the water to prevent the diffusion of suspended pollutants and protect the water environment. The protection efficiency of the bubble curtain is determined by the fusion of the bubble flow in the rising process and the stability of the plume under the action of a cross flow. The feasibility of a bubble curtain in field engineering is evaluated in this paper. Using two fluid models, the time-varying process of bubble fusion and migration in a bubble plume is analyzed. The dynamic behavior characteristics of the bubble plume are obtained, and the factors influencing the stability of the bubble plume are quantitatively described. The results show that the turbidity of the water body decreases in front of and behind the bubble curtain, which proves that the bubble curtain system is practical in dredging engineering. The number, size range and median value of bubbles in the flume are related to the ventilation pressure and pipe structure. There are three different phenomena in the half-width of the bubble plume at different heights. With the general linear model, it is concluded that the fusion height of the bubble plume is the most sensitive to the change in the bubble tube hole spacing and that the migration characteristics of the bubble plume are most significantly affected by the air flow at the bubble hole. The mechanical analysis of the plume stability shows that the Weber number is the most important parameter affecting the failure of the bubble curtain.