Gravity Current on Slope

Abstract

Gravity currents on slopes are studied by numerical experiments based on the finite volume solution of the Navier-Stokes equation. The head of the gravity current increases in volume, and the roll up of the interface and the mixing across it become violent with the slope. For steep slopes the enlarged head is divided from the subsequent current, the isolated head advances forward and accelerates to be divided again. The front is subject to the acceleration and deceleration repeatedly, but the acceleration effect of the gravity along the slope does not clearly appear in the fluctuated speed of the current front because the deceleration effect due to the enlargement of the head compensates for it. The average front speed increases with the angle of the slope in a range from zero, and reaches to the maximum speed at a certain angles of slope. At larger angle, the front speed decreases with the angles, which is caused by the division of the head and the violent mixing. It is elucidated that this variation of the front speed is associated with the change of the inner structure of the head from the parallel flow to the normal flow to the slope.