Experimental evaluation of two-layer air bubble curtains to prevent seawater intrusion into rivers

Abstract

The seawater intrusion (SWI) into rivers can lead to many negative consequences, especially on agricultural activities and live ecosystems in upstream areas of rivers. One solution to prevent SWI is using air bubble curtains (ABCs). The objective of this study is to investigate the optimal location of ABCs and airflows. To this end, several tests with different flow and salinity rates were performed and effect of ABC location on SWI investigated. The results show that, when the ratio of seawater to freshwater densities increased from 1.006 to 1.010, the ratio of saline wedge tip velocity to seawater velocity, airflow to seawater discharge ratio for first and second ABCs are raised 60, 58, and 70%, respectively. Also, when the Froude number (Fr) > 0.031, seawater density changes do not significantly affect the process of SWI. Besides, results of the study show that the closer the ABC is to the river downstream, the higher the airflow rates required. In addition, the optimal value of air bubbles for controlling SWI depends on the density of seawater, where more airflow is required to control denser flows. Finally, the regression equations to predict the SWI parameters based on flow properties were derived.