Numerical simulation of three-dimensional and bi-disperse particle-laden turbidity current in an experimental channel in presence of obstacle

In the present study, the propagation of a continuous three-dimensional, in the collision with obstacle and bi-disperse particle-laden turbidity current with a large eddy simulation method was modeled. Due to the presence of large number of suspended particles, the Eulerian-Eulerian method has been used and for each particle a concentration equation, which the particle settling velocity has been added to, is solved. The density current is simulated for particles with three different diameters 12, 20 and 30 microns. The inlet concentration effect of the particles has been studied by changing the inlet concentration to 0.6 and 0.3. The results show that in the same entrance conditions, before the obstacle, there is no significant change in the current speed profile in with and without obstacle state, but presence of an obstacle decreases the maximum velocity by 10%, also the amount of suspended particles on the obstacle decreases in channel width. In the final semi-stable state, the maximum concentration (after obstacle) 15.3% is reduced in compared to without obstacle state. By increasing the particle diameter to 20 and 30 microns, the maximum concentration is increased by 12.5% and 22.3%, the amount of suspended particles also decreases by 68% and 21%, respectively. As a result, particles with larger diameter precipitate more and rapidly and fine particles are transported over longer intervals by current. Changing the inlet concentration in the case of smaller diameter particle increases the amount of suspended particles by 11.2% and current will have more capability for carrying suspended particles.