Air flow effect on the behavior of lock-exchange gravity current

Document Type: Research Paper

Authors

1 Faculty of Mechanical engineering, University of Zanjan, Zanjan, Iran.

2 Amirkabir University Of Technology.

10.22055/jhs.2020.31685.1125

Abstract

The main goal of this study is investigating the effect of air flow above the free surface on the behavior of gravity current. Lock-release gravity current has been simulated in a channel, by using VOF method, for modeling free surface at the interface of gas and liquid phases. Eulerian approach is used to consider the presence of particles in the flow. The results of simulation with free surface assumption are in a well agreement with the previous experimental results. It is observed that the flows containing particles with larger diameter experience higher deposition rate, due to their higher terminal velocities which are 0.000129m/s, 0.000359m/s and 0.000808m/s for the particles with 12μm, 20μm and 30μm diameters respectively. Increasing the size of particles diameter leads to decrease in the driving force, the front position of flow containing particles with 30μm diameter is 11% less than that of flow containing particles with 12μm diameter, thereby the flow velocity decays quickly. The results show that the presence of particles leads to a reduction in the value of entrainment rate. It is concluded that the velocity of air-phase affects the shape of flow and instabilities. By considering three different values of 0.1m/s, 0.12m/s and 0.18m/s for the air-phase velocity, it is observed that the amount of run-out length, in the case where the air velocity is 0.18m/s, is nearly 3% more than that in other cases at the end of channel, moreover it leads to an increase in the value of entrainment rate.

Keywords


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