The effects of drag on turbulent gravity currents

We model the propagation of turbulent gravity currents through an array of obstacles which exert a drag force on the flow proportional to the square o f the flow speed. A new class of similarity solutions is constructed to des cribe the flows that develop from a source of strength q(0)t(gamma). An ana lytical solution exists for a finite release, gamma = 0, while power series solutions are developed for sources with gamma > 0. These are shown to pro vide an accurate approximation to the numerically calculated similarity sol utions. The model is successfully tested against a series of new laboratory experiments which investigate the motion of a turbulent gravity current th rough a large flume containing an array of obstacles. The model is extended to account for the effects of a sloping boundary. Finally, a series of geo physical and environmental applications of the model are discussed.