On the application of box models to particle-driven gravity currents

New laboratory experiments on different types of lock-exchange particle-dri ven gravity currents advancing into a flume of fresh water are presented. T hese include purely saline currents, monodisperse particle-laden gravity cu rrents with both fresh and saline interstitial fluid? and bidisperse partic le-laden currents. For each case a simple box model is developed. These agr ee well with the experimental data. We find that particulate gravity curren ts with saline interstitial fluid flowing into ambient fresh fluid are best described using a Froude number of 0.52 in the box model (cf. Huppert & Si mpson 1980). However, particulate gravity currents with fresh interstitial fluid are best described using a higher Froude number of 0.67. The change i n Froude number reflects the different shape and structure associated with the different density of interstitial fluid. For all experiments, box model s provide accurate predictions for up to twenty lock-lengths.