Experimental investigation of the effect of obstacles on the behavior of turbidity currents

Abstract

Turbidity current is produced when a particle-laden fluid flows under lighter ambient fresh fluid. The streaming of particle-laden fluid is called a turbidity current and this kind of current is an important mechanism for sediment transportation in lakes and oceans. In the present research, the main concentration is on the effect of obstacle with an isosceles right triangular cross section on the behavior of turbidity current. A series of laboratory experiments were carried out with various obstacle heights and different inlet densimetric Froude numbers. In each experiment, velocity profiles upstream and downstream of the obstacle were measured, using an acoustic Doppler velocimeter. Kaolin was used as the suspended material. Experiments showed that the density current with lower inlet Froude number, reacts to the presence of the obstacle more rapidly compared to the currents with higher values of inlet Froude number. At the upstream section of the obstacle, an increase in the height of the obstacle resulted in a reduction in the current inertia and the maximum velocity. Also the local Froude numbers had an abrupt increase when the dense layer passed the obstacle.