Propagation and flow structure of turbidity currents in settling regimes: A Lagrangian particle-tracking study

Numerical simulations are performed to investigate the propagation, flow structure, and runout of turbidity currents in regimes where buoyancy-driven dynamics interact with finite settling effects. A Lagrangian particle-tracking framework is used to represent the evolving density field and its coupling with the carrier flow, enabling detailed analysis of current dynamics across multiple flow regimes. 

We first examine the temporal evolution of turbidity currents, which exhibit distinct slumping, propagation, and dissipation stages. The role of finite settling is shown to modulate density stratification and, in turn, the efficiency of momentum transfer within the current. We then analyse flow structure and deposition-induced feedbacks on the current dynamics. Transverse variations in the flow and deposition pattern are associated with lobe-and-cleft structures, while longitudinal variations arise from vortex detachment and decay. Finally, we propose a new scaling law for turbidity-current propagation speed and runout length that incorporates the combined effects of buoyancy forcing and settling-induced density evolution. The numerical results show close agreement with the proposed scaling, supporting its applicability to a wide class of particle-laden density currents. These results provide new insight into the dynamics of turbidity currents as geophysical density currents and contribute to improved predictive frameworks for buoyancy-driven flows in natural environments.