Discussion of "Mahmodinia, S., & Javan, M. (2021). Vortical structures, entrainment and mixing process in the lateral discharge of the gravity current. Environmental Fluid Mechanics, 21(5), 1035-1067"

Abstract

The authors of the discussed paper presented an interesting study of the lateral gravity currents for the different flow conditions. The authors showed the three-dimensional (3D) turbulent structures at the channel junction. The discussed paper utilized the transient Reynolds-Averaged Navier-Stokes (RANS) equations to visualize the 3D turbulent structures. The present discussion paper shows that the choice of the transient RANS is not appropriate for investigating the 3D turbulent structures at the channel junction. The current discussion paper compares the performance of the transient RANS model and eddy-resolving Detached eddy simulation model in predicting the characteristics 3D turbulent structures at the junction. The comparisons show that the transient RANS model is unable to capture the breakdown of the sheet-shaped turbulent structure due to Kelvin-Helmholtz instability when the flow from the lateral channel separates at the sharp downstream junction corner.