Slumping regime in lock-release turbidity currents

TL;DR

This study experimentally investigates the slumping regime of turbidity currents on inclined slopes, identifying regimes controlled by particle settling and current inertia, and analyzing their dynamics and velocity behaviors.

Contribution

It provides a comprehensive experimental analysis of turbidity current regimes, highlighting the influence of particle settling and slope on current morphology and velocity.

Findings

Three regimes controlled by settling and inertia ratios.

Velocity increases with slope up to 15° in certain regimes.

Water entrainment coefficient E increases linearly with Reynolds number.

Abstract

Most gravitational currents occur on sloping topographies, often in the presence of particles that can settle during the current propagation. Yet, an exhaustive exploration of associated parameters in experimental studies is still lacking. Here, we present an extensive experimental investigation of the slumping regime of turbidity (particle-laden) currents in two lock-release (dam-break) systems with inclined bottoms. We identify 3 regimes controlled by the ratio between settling and current inertia. (i) For negligible settling, the turbidity current morphodynamics correspond to those of saline homogeneous gravity currents, in terms of velocity, slumping (constant-velocity) regime duration and current morphology. (ii) For intermediate settling, the slumping regime duration decreases to become fully controlled by a particle settling characteristic time. (iii) When settling overcomes the current initial inertia, the slumping (constant-velocity) regime is not detected any more. In the first two regimes, the current velocity increases with the bottom slope, of about $35~\%$ between $0^\circ$ and $15^\circ$. Finally, our experiments show that the current propagates during the slumping regime with the same shape in the frame of the moving front. Strikingly, the current head is found to be independent of all experimental parameters covered in the present study. We also quantify water entrainment coefficients $E$ and compare them with previous literature, hence finding that $E$ increases linearly with the current Reynolds number.