Thermally enhanced gravity driven flows

Gravity currents play a major role in both natural and human-made settings. The driving buoyancy forces for these flows are due to density differences which may arise as a result of compositional differences (e.g. salinity), the presence of suspended material in the flow as in the case of turbidity currents, temperature differences, or a combination of these mechanisms. This article reports on a study of surface gravity currents moving horizontally over a slightly denser ambient fluid when these surface layers are subjected to an incoming heat flux which acts to enhance (or erode) the existing stratification. A general equation of state is adopted to connect the density of the upper layer to its changing temperature. A two-layer hydraulic theory is developed and conditions for its validity carefully specified. Both analytical and numerical analyses are carried out in order to examine the salient features of these flows.