Abstract
Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.
Highlights
Turbidity currents are buoyancy-driven underflows generated by the action of gravity on the density difference between a fluid-sediment mixture and the ambient fluid
The excess hydrostatic pressure within the turbidity current drives the current downstream while complicated interactions with the surrounding environment take place; it interacts with the ambient fluid at the upper boundary and with the bed at the lower boundary, producing turbulence at both boundaries [1]
We examine here the capability of the model to capture the internal density distribution of the flow through comparing concentration profiles measured with Conductivity-type Concentration Meter (CCM) along different inclinations versus numerical results
Summary
Turbidity currents are buoyancy-driven underflows generated by the action of gravity on the density difference between a fluid-sediment mixture and the ambient fluid. Laboratory experiments are widely used (e.g., [14,15,16,17]) and can be scaled and conducted under more controlled conditions to develop a better understanding of the behavior of turbidity currents, and to provide measurements for the validation of numerical models To this end, Alhaddad et al [18] have recently conducted large-scale experiments, obtaining direct measurements of breaching-generated turbidity currents and the associated sediment transport. Alhaddad et al [3] applied the one-dimensional model of [26] to a typical case of a breaching slope, demonstrating that the results are highly sensitive to the type of breaching closure relation used To reduce these uncertainties, this study presents large eddy simulations of breaching-generated turbidity currents.
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