EFFECTS OF EXTERNAL FLOW ON COMPOSITIONAL AND PARTICLE GRAVITY CURRENTS

The propagation at high Reynolds number of a heavy, two-dimensional gr avity current of given initial volume at the base of a uniform flow is considered. An experimental setup is described for which a known volu me of fluid is rapidly introduced halfway down a 9m channel in which t here is a uniform flow of water. The density excess of the released fl uid is produced by either dissolving salt or suspending particles in w ater. The upstream and downstream propagation of the current was measu red for different initial salt concentrations, particle sizes and conc entrations. A simple box model for the motion of and deposit from the gravity current is constructed. The analytical results obtained compar e well with our numerical solutions of one-layer and two-layer models incorporating the appropriate shallow-water equations. Both sets of re sults are in very good agreement with the experimental data.