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Title: Variable density mixing in turbulent jets with coflow

Abstract

Two sets of experiments are performed to study variable-density effects in turbulent round jets with co flow at density ratios, s = 4.2 and s = 1.2. 10,000 instantaneous realisations of simultaneous 2-D PIV and PLIF at three axial locations in the momentumdominated region of the jet allow us to calculate the full t.k.e. budgets, providing insights into the mechanisms of density fluctuation correlations both axially and radially in a non- Boussinesq flow. The strongest variable-density effects are observed within the velocity half-width of the jet, r ~u1/2 . Variable density effects decrease the Reynolds stresses via increased turbulent mass flux in the heavy jet, as shown by previous jet centreline measurements. Radial pro les of turbulent flux show that in the lighter jet t.k.e. is moving away from the centreline, while in the heavy jet it is being transported both inwards towards the centreline and radially outwards. Negative t.k.e. production is observed in the heavy jet, and we demonstrate that this is caused by both reduced gradient stretching in the axial direction and increased turbulent mass fluxes. Large differences in advection are also observed between the two jets. The air jet has higher total advection caused by strong axialmore » components, while density fluctuations in the heavy jet reduce the axial advection signi cantly. The budget mechanisms in the non-Boussinesq regime are best understood using effective density and velocity half-width, ρeff ¯u 3 1,CL/r ~u1/2,eff , a modi cation of previous scaling.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10)
OSTI Identifier:
1374317
Report Number(s):
LA-UR-16-24522
Journal ID: ISSN 0022-1120
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Fluid Mechanics
Additional Journal Information:
Journal Volume: 825; Journal ID: ISSN 0022-1120
Publisher:
Cambridge University Press
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats

Charonko, John James, and Prestridge, Katherine Philomena. Variable density mixing in turbulent jets with coflow. United States: N. p., 2017. Web. doi:10.1017/jfm.2017.379.
Charonko, John James, & Prestridge, Katherine Philomena. Variable density mixing in turbulent jets with coflow. United States. doi:10.1017/jfm.2017.379.
Charonko, John James, and Prestridge, Katherine Philomena. Mon . "Variable density mixing in turbulent jets with coflow". United States. doi:10.1017/jfm.2017.379. https://www.osti.gov/servlets/purl/1374317.
@article{osti_1374317,
title = {Variable density mixing in turbulent jets with coflow},
author = {Charonko, John James and Prestridge, Katherine Philomena},
abstractNote = {Two sets of experiments are performed to study variable-density effects in turbulent round jets with co flow at density ratios, s = 4.2 and s = 1.2. 10,000 instantaneous realisations of simultaneous 2-D PIV and PLIF at three axial locations in the momentumdominated region of the jet allow us to calculate the full t.k.e. budgets, providing insights into the mechanisms of density fluctuation correlations both axially and radially in a non- Boussinesq flow. The strongest variable-density effects are observed within the velocity half-width of the jet, r~u1/2 . Variable density effects decrease the Reynolds stresses via increased turbulent mass flux in the heavy jet, as shown by previous jet centreline measurements. Radial pro les of turbulent flux show that in the lighter jet t.k.e. is moving away from the centreline, while in the heavy jet it is being transported both inwards towards the centreline and radially outwards. Negative t.k.e. production is observed in the heavy jet, and we demonstrate that this is caused by both reduced gradient stretching in the axial direction and increased turbulent mass fluxes. Large differences in advection are also observed between the two jets. The air jet has higher total advection caused by strong axial components, while density fluctuations in the heavy jet reduce the axial advection signi cantly. The budget mechanisms in the non-Boussinesq regime are best understood using effective density and velocity half-width, ρeff ¯u3 1,CL/r~u1/2,eff , a modi cation of previous scaling.},
doi = {10.1017/jfm.2017.379},
journal = {Journal of Fluid Mechanics},
number = ,
volume = 825,
place = {United States},
year = {2017},
month = {7}
}

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