Helical flow couplets in submarine gravity underflows

Active and relic meandering channels are common on the seafloor adjacent to continental margins. These channels and their associated submarine fan deposits are products of the density-driven gravity flows known as turbidity currents. The tie between channel curvature and its effects on these gravity flows has been an enigma. This paper records the results of both large-scale laboratory measurements and a numerical simulation that captures the three-dimensional flow field of a gravity underflow at a channel bend. These findings reveal that channel curvature drives two helical flow cells, one stacked upon the other. The lower cell forms near the channel bed surface and has a circulation pattern similar to that observed in fluviall channels, i.e., with a near-bed flow directed inward. The other circulation cell forms in the upper part of the gravity flow and has a streamwise vorticity with the opposite sense of the lower cell.