Effect of bed slope on turbidity currents interacting with an obstacle
Insights from Large Eddy Simulations
Said Alhaddad (TU Delft - Mechanical Engineering)
Ching Sen Wu (National Ilan University)
Lynyrd de Wit (Deltares)
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Abstract
Understanding the behavior of turbidity currents is crucial for the effective and sustainable management of natural and artificial hydraulic systems. This study employs a high-resolution numerical model based on the Large Eddy Simulation (LES) approach to investigate the effect of bed slope on the dynamics and depositional behavior of turbidity currents interacting with a triangular obstacle in a channel. Six bed slopes were studied ranging from 0% to 4.5%. Our analysis focused mostly on the quasi-steady-state flow conditions upstream of the obstacle. The results reveal that steeper slopes enhance sediment transport capacity, leading to reduced sediment deposition rates along the bed and thus a decline in the obstacle's sediment-retention efficiency. The increased transport capacity primarily results from higher flow velocities rather than increased sediment concentrations. Detailed analysis of velocity distributions upstream of the obstacle, under quasi-steady state, showed that the velocity profiles are distorted differently among bed slopes as a result of the interplay between flow inertia and the adverse pressure gradient induced by the obstacle. Recirculation zones are observed for the milder bed slopes (0–1.5%), whereas these zones disappear for steeper slopes (3–4.5%), indicating the dominance of inertial effects.
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