Gravity currents with large salinity in a gravel bed valley: an experimental study

Abstract

In the current study experiments in a valley (a composite cross-sectional tank consisting of a rectangular upper cross section and a lower trapezoidal) were performed. The purpose of this research is to study the gravel bed in gravity currents with large salinity. The tank is separated in two parts by a vertical gate, which separates the fresh water with the gravel bed from the salt water with the impermeable bed. When the gate opens, a flow is created due to density difference. The salinity densities are large (from 1,050 to 1,090 kg/m3). These specific densities have been chosen to simulate liquid wastes that affect the environment. Compared to experiments in the same tank without a gravel bed, it is observed that the gravel bed reduces the propagation of currents and mainly reduces the current with the smallest density difference at the lowest height. The main conclusion of this study is that the kind of channel bed plays a key role in the propagation of gravity currents. The gravel bed affects significantly the velocity and the distance traveled by the currents in comparison with impermeable bed. HIGHLIGHTS Lock-exchange experiments were performed in a tank of composite cross section.; The tank had a trapezoidal cross-section at its lower part and rectangular in its upper part.; It was discovered that the kind of channel plays a key role in the propagation of gravity currents.; The motion of gravity current in the case of an impermeable bed differs significantly from the case of a permeable (gravel) bed.;

Keywords

• front velocity
• gravel bed
• gravity currents
• large salinity
• lock-exchange experiments