Dynamics of lock-release crystalline gravity currents

Coastal and marine environments are impacted by inflows of varying types and chemical compositions. This novel study experimentally investigated the dynamics of a particular type of inflow—crystalline gravity currents (CGC) produced by the lock release of over-saturated brine solutions (i.e., they contain a proportion of suspended salt crystals) into a non-stratified ambient. Such flows may occur from desalination and chemical plant discharges. CGCs were found to show two distinguishing characteristics from normal under-saturated gravity currents (UGC). One was that CGCs have longer slumping distances than UGC while the other was that during the self-similar phase, CGCs have a decreasing trend in their velocities, and the current’s height is no longer constant. These differences result because the CGCs drop crystals onto the bed as they advance. Their flow behaviour was also found to be dependent on the flow head density or local density; whereas, UGC flow is a function of the initial fluid density. This unique study gives a significant insight into crystalline gravity currents showing how they can impact the coastal environments they are encountered in, e.g., the discharge vicinity of desalination and chemical plants.