Towards a universal criteria for turbulence suppression in dilute turbidity currents with non‐cohesive sediments

Abstract

[1] Turbidity currents exhibit fascinating physics as their sustained propagation depends on a tight interplay between the suspended sediments and turbulence. If resuspension dominates over deposition the intensity of the flow will increase, while if deposition dominates the flow turbulence can be completely damped inducing rapid settling of sediments and, eventually, flow extinction. This work explores the phenomenon whereby turbulence in a dilute turbidity current with non-cohesive sediments is abruptly extinguished owing to increased suspended sediment stratification. Three parameters control the flow dynamics: Reynolds number (Re t ), Richardson number (Ri t ) and sediment settling velocity (Ṽ z ). The condition for complete turbulence suppression can be expressed as a critical value for Ri tṼ z . Based on simulations, limited experiments and limited field data, the critical value appears to have a logarithmic dependence on Re t . Citation: Cantero, M. I., M. Shringarpure, and S. Balachandar (2012), Towards a universal criteria for turbulence suppression in dilute turbidity currents with non-cohesive sediments, Geophys.

Effect of self-stratification on sediment diffusivity in channel flows and boundary layers: a study using direct numerical simulations

“…Dutta (2012) showed that increase in eitherṼ or Ri τ increases the degree of self-stratification caused by suspended sediment and the extent to which a flow will stratify depends on the parameter V Ri τ . Cantero et al (2012) made similar observations for turbidity currents. In Figs. 2 and 3 the mean streamwise velocity, steady-state sediment concentration profile and normalized wall-normal turbulence intensity for set1 and set2 have been plotted.…”

Physical theory for near-bed turbulent particle suspension capacity

“…The turbulence extinction threshold of Cantero et al (2009Cantero et al ( , 2011Cantero et al ( , 2012 is virtually identical to = 1 (Fig. 3b).…”

“…An apparent reduction in turbulence with increasing particle concentration is the result of a portion of this budget having been expended in maintaining particle suspension (Tilston, 2016). Both Bennett et al (2014) and Cantero et al (2012) invoke a similar expenditure of turbulent kinetic energy (TKE), arguing that part of the TKE is consumed or transferred from turbulent fluid to particles in order to keep them suspended. The interpretation presented here differs slightly in that we argue that the presence of suspended particles prevents part of the turbulence from ever being produced.…”

“…Turbulence extinction at over-saturation must be expected to result in sedimentation as there is no mechanism countering gravitational settling of sediment. This second perspective is reminiscent of a recent breakthrough in DNSs of suspension flows (Cantero et al, 2009(Cantero et al, , 2011(Cantero et al, , 2012) that demonstrates how turbulence at the base of suspension flows is rapidly extinguished in over-saturated suspensions. The studies by Cantero and co-workers demonstrate that the complete suppression of turbulence at oversaturation is related to the disappearance of the streak vortices that form the legs of hairpin vortices.…”

“…3, results in rapid deposition from the base of the flow and a return to capacity transport. Data from studies with saturated suspensions (Bennett et al, 1998; (Cantero et al, 2009(Cantero et al, , 2011(Cantero et al, , 2012 and balanced sedimentation-entrainment fluxes (Garcia and Parker, 1993 Coleman, 1986;Graf and Cellino, 2002;Smith and McLean, 1977) lie around = 1. = 1 also envelopes the upper range of data points from Vanoni (1940), Einstein and Chien (1955;reported in Montes Videla, 1973), Ordoñez (1970;reported in Montes Videla, 1973), and Montes Videla (1973).…”