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Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface
In this work we study the turbulence modulation in a viscosity-stratified two-phase flow using Direct Numerical Simulation (DNS) of turbulence and the Phase Field Method (PFM) to simulate the interfacial phenomena. Specifically we consider the case of two immiscible fluid layers driven in a closed r...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Springer Netherlands
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044243/ https://www.ncbi.nlm.nih.gov/pubmed/30069147 http://dx.doi.org/10.1007/s10494-018-9918-2 |
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author | Ahmadi, Somayeh Roccon, Alessio Zonta, Francesco Soldati, Alfredo |
author_facet | Ahmadi, Somayeh Roccon, Alessio Zonta, Francesco Soldati, Alfredo |
author_sort | Ahmadi, Somayeh |
collection | PubMed |
description | In this work we study the turbulence modulation in a viscosity-stratified two-phase flow using Direct Numerical Simulation (DNS) of turbulence and the Phase Field Method (PFM) to simulate the interfacial phenomena. Specifically we consider the case of two immiscible fluid layers driven in a closed rectangular channel by an imposed mean pressure gradient. The present problem, which may mimic the behaviour of an oil flowing under a thin layer of different oil, thickness ratio h(2)/h(1) = 9, is described by three main flow parameters: the shear Reynolds number Re(τ) (which quantifies the importance of inertia compared to viscous effects), the Weber number We (which quantifies surface tension effects) and the viscosity ratio λ = ν(1)/ν(2) between the two fluids. For this first study, the density ratio of the two fluid layers is the same (ρ(2) = ρ(1)), we keep Re(τ) and We constant, but we consider three different values for the viscosity ratio: λ = 1, λ = 0.875 and λ = 0.75. Compared to a single phase flow at the same shear Reynolds number (Re(τ) = 100), in the two phase flow case we observe a decrease of the wall-shear stress and a strong turbulence modulation in particular in the proximity of the interface. Interestingly, we observe that the modulation of turbulence by the liquid-liquid interface extends up to the top wall (i.e. the closest to the interface) and produces local shear stress inversions and flow recirculation regions. The observed results depend primarily on the interface deformability and on the viscosity ratio between the two fluids (λ). |
format | Online Article Text |
id | pubmed-6044243 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | Springer Netherlands |
record_format | MEDLINE/PubMed |
spelling | pubmed-60442432018-07-30 Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface Ahmadi, Somayeh Roccon, Alessio Zonta, Francesco Soldati, Alfredo Flow Turbul Combust Article In this work we study the turbulence modulation in a viscosity-stratified two-phase flow using Direct Numerical Simulation (DNS) of turbulence and the Phase Field Method (PFM) to simulate the interfacial phenomena. Specifically we consider the case of two immiscible fluid layers driven in a closed rectangular channel by an imposed mean pressure gradient. The present problem, which may mimic the behaviour of an oil flowing under a thin layer of different oil, thickness ratio h(2)/h(1) = 9, is described by three main flow parameters: the shear Reynolds number Re(τ) (which quantifies the importance of inertia compared to viscous effects), the Weber number We (which quantifies surface tension effects) and the viscosity ratio λ = ν(1)/ν(2) between the two fluids. For this first study, the density ratio of the two fluid layers is the same (ρ(2) = ρ(1)), we keep Re(τ) and We constant, but we consider three different values for the viscosity ratio: λ = 1, λ = 0.875 and λ = 0.75. Compared to a single phase flow at the same shear Reynolds number (Re(τ) = 100), in the two phase flow case we observe a decrease of the wall-shear stress and a strong turbulence modulation in particular in the proximity of the interface. Interestingly, we observe that the modulation of turbulence by the liquid-liquid interface extends up to the top wall (i.e. the closest to the interface) and produces local shear stress inversions and flow recirculation regions. The observed results depend primarily on the interface deformability and on the viscosity ratio between the two fluids (λ). Springer Netherlands 2018-04-25 2018 /pmc/articles/PMC6044243/ /pubmed/30069147 http://dx.doi.org/10.1007/s10494-018-9918-2 Text en © The Author(s) 2018 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. |
spellingShingle | Article Ahmadi, Somayeh Roccon, Alessio Zonta, Francesco Soldati, Alfredo Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title | Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title_full | Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title_fullStr | Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title_full_unstemmed | Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title_short | Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface |
title_sort | turbulent drag reduction by a near wall surface tension active interface |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044243/ https://www.ncbi.nlm.nih.gov/pubmed/30069147 http://dx.doi.org/10.1007/s10494-018-9918-2 |
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