Shear-flow dispersion in turbulent jets
File(s)
Published version
Author(s)
Craske, J
Debugne, ALR
van Reeuwijk, M
Type
Journal Article
Abstract
We investigate the transport of a passive scalar in a fully developed turbulent axisymmetric jet at a Reynolds number of Re = 4815 using data from direct numerical simulation. In particular, we simulate the response of the concentration field to an instantaneous variation of the scalar flux at the source. To analyse the time evolution of this statistically
unsteady process we take an ensemble average over 16 independent simulations. We find that the evolution of Cm(z, t), the radial integral of the ensemble-averaged concentration, is a self-similar process, with front position and spread both scaling as √t. The longitudinal mixing of Cm is shown to be primarily caused by shear-flow dispersion.
Using the approach developed by Craske & van Reeuwijk (J. Fluid Mech., vol. 763, 2014,
pp. 538–566), the classical theory for shear-flow dispersion is applied to turbulent jets to obtain a closure that couples the integral scalar flux to the integral concentration Cm. Model predictions using the dispersion closure are in good agreement with the simulation data. Application of the dispersion closure to a two-dimensional jet results in an integral
transport equation that is fully consistent with that of Landel et al. (J. Fluid Mech., vol.711, 2012, pp. 212–258)
unsteady process we take an ensemble average over 16 independent simulations. We find that the evolution of Cm(z, t), the radial integral of the ensemble-averaged concentration, is a self-similar process, with front position and spread both scaling as √t. The longitudinal mixing of Cm is shown to be primarily caused by shear-flow dispersion.
Using the approach developed by Craske & van Reeuwijk (J. Fluid Mech., vol. 763, 2014,
pp. 538–566), the classical theory for shear-flow dispersion is applied to turbulent jets to obtain a closure that couples the integral scalar flux to the integral concentration Cm. Model predictions using the dispersion closure are in good agreement with the simulation data. Application of the dispersion closure to a two-dimensional jet results in an integral
transport equation that is fully consistent with that of Landel et al. (J. Fluid Mech., vol.711, 2012, pp. 212–258)
Date Issued
2015-10-25
Date Acceptance
2015-07-17
Citation
Journal of Fluid Mechanics, 2015, 781, pp.28-51
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
28
End Page
51
Journal / Book Title
Journal of Fluid Mechanics
Volume
781
Copyright Statement
© 2015 Cambridge University Press This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/J500239/1
Subjects
jets
mixing
turbulence simulation
Publication Status
Published
Date Publish Online
2015-09-16