Laboratory study of dense gravity current propagation over porous bed layers

Results are presented for a series of laboratory experiments investigating the propagation characteristics of dense gravity currents over porous bed layers comprising of fine sand (FS), coarse sand (CS) and a sand-gravel (SG) mixture. Gravity currents were generated via a lock-release system and the resulting current propagation was measured by tracking the frontal position over time with high-resolution digital cameras. Dense water intrusion into the porous bed layers was also monitored via an array of electrodes that measured temporal changes in the electrical resistance of the pore fluids. Results indicated that the temporal evolution of the gravity current front was slower over the CS and SG beds, compared to over the FS bed. Resistance measurements illustrated that the time scale for brine intrusion was comparable with the frontal propagationtime scales over the CS and SG beds, but was considerably longer within the FS bed runs.