@article{van:2014:10.1017/jfm.2013.613,
author = {van, Reeuwijk M and Holzner, M},
doi = {10.1017/jfm.2013.613},
journal = {Journal of Fluid Mechanics},
pages = {254--275},
title = {The turbulence boundary of a temporal jet},
url = {http://dx.doi.org/10.1017/jfm.2013.613},
volume = {739},
year = {2014}
}

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TY  - JOUR
AB  - We examine the structure of the turbulence boundary of a temporal plane jet at Re=5000 using statistics conditioned on the enstrophy. The data is obtained by direct numerical simulation and threshold values span 24 orders of magnitude, ranging from essentially irrotational fluid outside the jet to fully turbulent fluid in the jet core. We use two independent estimators for the local entrainment velocity vn based on the enstrophy budget. The data show clear evidence for the existence of a viscous superlayer (VSL) that envelopes the turbulence. The VSL is a nearly one-dimensional layer with low surface curvature. We find that both its area and viscous transport velocity adjust to the imposed rate of entrainment so that the integral entrainment flux is independent of threshold, although low-Reynolds-number effects play a role for the case under consideration. This threshold independence is consistent with the inviscid nature of the integral rate of entrainment. A theoretical model of the VSL is developed that is in reasonably good agreement with the data and predicts that the contribution of viscous transport and dissipation to interface propagation have magnitude 2vn and −vn , respectively. We further identify a turbulent core region (TC) and a buffer region (BR) connecting the VSL and the TC. The BR grows in time and inviscid enstrophy production is important in this region. The BR shows many similarities with the turbulent–non-turbulent interface (TNTI), although the TNTI seems to extend into the TC. The average distance between the TC and the VSL, i.e. the BR thickness is about 10 Kolmogorov length scales or half a Taylor length scale, indicating that intense turbulent flow regions and viscosity-dominated regions are in close proximity.
AU  - van,Reeuwijk M
AU  - Holzner,M
DO  - 10.1017/jfm.2013.613
EP  - 275
PY  - 2014///
SN  - 0022-1120
SP  - 254
TI  - The turbulence boundary of a temporal jet
T2  - Journal of Fluid Mechanics
UR  - http://dx.doi.org/10.1017/jfm.2013.613
UR  - http://arxiv.org/abs/1304.0476
UR  - https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/abs/turbulence-boundary-of-a-temporal-jet/4C5A64C47E24A28316F03295CB965746
VL  - 739
ER  - 

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