The Effect of Flexible Vegetation in Gravity Currents with Large Salinity in Composite Cross Section

Abstract

In this study experiments in a laboratory tank to examine the effect of bed with vegetation on the motion of gravity currents between fresh and salt water with high salinity were performed. The shape of the tank was composite (trapezoidal at the bottom and rectangular at the top). The tank was separated into two reservoirs with a vertical gate. One of the reservoirs was filled with salt water (sw) with various densities from 1050 till 1090 kg/m3. These values of densities simulates and represents the spread of liquid waste. The release of pollutants into rivers and wetlands, the spread of an oil spill into the ocean are examples of gravity currents that have detrimental environmental consequences. The second reservoir was filled with fresh water (w) and vegetation at the bed. When the gate is opened, the heavier liquid propagates towards the tank with the lightest liquid which is displaced along the free surface in the opposite direction. The results showed that the shape of the valley plays a very important role on the front velocity of gravity currents. The low water height and the presence of trapezoidal shape decreases the velocity of the gravity current. The increase of the initial height (for fresh and high salinity water) also produces gravity currents with higher velocity. © 2021, The Society for Experimental Mechanics, Inc.