Curvature-induced secondary flow in submarine channels

The curvature-driven secondary flow in sinuous submarine channels has been a subject of considerable interest and controversy. Here, results from numerical model studies involving saline flow in laboratory-scale channels are presented. A 3D finite volume model of density and turbidity currents is used and simulations are run with different inflow discharges and channel-axis slopes. The simulation results show strong influence of bend wave length, channel gradient, confinement and cross sectional shape on the structure of secondary flow in submarine channels. Major findings are: (i) reversal of secondary flow in submarine channels is strongly associated with a tight bend characterized by a smaller wave length to width ratio or larger wave number, (ii) for the same inflow condition and planform characteristics, a trapezoidal channel cross section is more favorable to secondary flow reversal than a rectangular cross section, (iii) lateral convection resulting from the interaction between in-channel and overbank flows leads to the reversal of secondary flow in an unconfined channel at a lower channel slope than in a confined channel with the same dimensions, (iv) flow discharge has only nominal effect on the secondary flow in submarine channels.