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Gravity currents modify their flow characteristics in the presence of an obstacle. Also, the flow path to the dam reservoirs is not always direct. Since no studies have addressed the feedback between the hydrodynamics of a gravity current in a curved channel and the location effects of the obstacle, in this research, a Lock-exchange density current flows in a 120${}^{\circ }$ bending channel. The numerical simulation has been performed using OpenFOAM software. The models include no-obstacle curved channel and a curved channel with an obstacle in different positions concerning the increased radius of the curved channel. Results indicated that the obstacle directed the concentration towards the banks, with its maximum value tending from the outer to the inner bank, especially in the tail. The tail longitudinal velocity maximized near the channel bed in areas far from the obstacle, and in the outer bank in areas near it. The secondary flow reduces its lowest and most different pattern observed around the obstacle. In displacing the latter, if the front has at a certain distance, the secondary flow does not change much, but if it has at the channel end, the post-obstacle secondary flow would increase as the obstacle neared the Lock.

The mixing within a full depth lock-exchange gravity current was investigated experimentally with planar laser-induced fluorescence PLIF. The scalar edge of the gravity current was identified via an edge detection algorithm. A strong mixing region located along this edge was extracted from the flow field and analyzed. A dimensionless background potential energy was defined to characterize the local mixing rate in this region, which showed a two-stage behavior. In the section near the nose, mixing rate oscillates strongly under the influence of the lobe and cleft shifting, while in the upper part, the mixing rate grows gradually under the mechanism of billows rolling up.

In this work we address the frontal instability of gravity currents. The planar laser-induced fluorescence (PLiF) flow visualization is utilized to analyze the detailed dynamics of the current, which are generated in a lock-exchange Perspex tank. We believe that two dominant modes of instability determine the complex structures at the head of the flow. The first one resembles Kelvin–Helmholtz instability, which results in Kelvin–Helmholtz billows rolling up in the shear zone above the head. The other, categorized as convective instability known as "lobes and clefts", which stems from ground friction as well as unstable inverse density stratification, and is considered to be the cause for the disruption of the span-wise symmetry of Kelvin–Helmholtz billows. Moreover, our observations indicate that the convective instability also contributes to a secondary instability associated with Kelvin–Helmholtz vortex breakdown. These instabilities not only play a central role in shaping the three-dimension characteristics of the currents, but also govern the mixing and entrainment mechanisms. Therefore, more precise measurement of the positions of the frontal instability and the flow structures, especially the turbulent structures is indeed necessary.