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Observations of the turbulent fluxes of suspended sand near the sea-bed
Published in W. Bechteler, Transport of Suspended Solids in Open Channels, 2022
R.L. Soulsby, A.P. Salkield, R.A. Haine, B. Wainwright
It is known that in stably stratified flows the (eddy diffusivity)/(eddy viscosity) ratio becomes progressively smaller as the stratification increases (Odd and Rodger, 1978). In the present case density stratification is produced by the suspended sediment, with the degree of stratification being quantified by the gradient Richardson number given by: Ri=g(ρs−ρ)(C¯13−C¯33)Δzρsρ(U¯13−U¯33)2
Water Balances and Multidimensional Models
Published in James L. Martin, Steven C. McCutcheon, Robert W. Schottman, Hydrodynamics and Transport for Water Quality Modeling, 2018
James L. Martin, Steven C. McCutcheon, Robert W. Schottman
where βM is an empirical coefficient. Based on the Boussinesq assumption that may be questionable in stratified flows, many investigators have assumed that formulations for vertical turbulent diffusivities are equivalent in form to eddy viscosity equations.
CFD study of oil-water segregated and dispersed flow coalescence in horizontal pipes
Published in Chemical Engineering Communications, 2021
Juan Carlos Berrio, Andres Pinilla, Nicolas Ratkovich
In general terms, flow patterns can be classified into three categories: (i) stratified or segregated, (ii) dispersed, and (iii) intermittent flow. A representation of these three categories is shown in Figure 1. In stratified flows, is when the two phases (oil and water) are segregated by gravity, where the high dense fluid (water) flows below the less dense fluid (oil), with interphase between water and oil, this flow pattern mainly appears at low mixture velocities. Nevertheless, this interphase can be smooth, wavy, or mixed with droplets of both water-in-oil and/or oil-in-water. A non-stratified flow can occur with the presence of phase droplets of either within the oil or water phase that exists continuously as the mixture flows throughout the pipe. Non-stratified flow also is known as a dispersed flow. Furthermore, the latter, the intermittent flows are characterized by having large oil droplets separated by water slugs, generated when the mixture velocity increases (Bannwart et al. 2004).
Investigation of the interfacial instability in a non-Boussinesq density stratified flow using linear stability theory
Published in Cogent Engineering, 2019
Ehsan Khavasi, Pouriya Amini, Javad Rahimi, Mohammad Hadi Mohammadi
Interfacial instabilities affect the behavior of stratified flows. An improved understanding of the interfacial instabilities in stratified shear flows can aid to forecast exchange flow rates and vertical mixing rates. The importance of this forecasting is because of its control on the vertical transfer of salt, heat, nutrients, pollutants and momentum in stratified flows. A noteworthy quantity of mixing in the interior ocean and atmosphere is produced by the formation of shear instabilities in density stratified flows (Nourmohammadi, Afshin, & Firoozabadi, 2011). It is probable to predict instabilities using linear stability analysis. The results of such tool provide a theoretical estimation of initial instability frequency or wavelength, the instability growth rate, knowledge that is serious for understanding and controlling shear flows (Khavasi & Firoozabadi, 2018, 2019).