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Self-similar properties of decelerating turbulent jets

Self-similar properties of decelerating turbulent jets
Self-similar properties of decelerating turbulent jets
The flow in a decelerating turbulent round jet is investigated using direct numerical simulation. The simulations are initialised with a flow field from a statistically-stationary turbulent jet. Upon stopping the inflow, a deceleration wave passes through the jet, behind which the velocity field evolves towards a new statistically-unsteady self-similar state. Assumption of unsteady self-similar behaviour leads to analytical relations concern-ing the evolution of the centreline mean axial velocity and the shapes of the radial profiles of the velocity statistics. Consistency between these predictions and the simulation data supports the use of the assumption of self-similarity. The mean radial velocity is predicted to reverse in direction near to the jet centreline as the deceleration wave passes, contributing to an approximately three-fold increase in the normalised mass entrainment rate. The shape of the mean axial velocity profile undergoes a relatively small change across the deceleration transient, and this observation provides direct evidence in support of previous models that have assumed that the mean axial velocity profile, and in some cases also the jet spreading angle, remain approximately constant within unsteady jets.
0022-1120
R1
Shin, Dong-Hyuk
aefc1292-87fd-48ab-94bc-a857692ccabe
Aspden, Andrew
7353e0e9-fbed-4f5a-a610-b045cd4cd576
Richardson, Edward
a8357516-e871-40d8-8a53-de7847aa2d08
Shin, Dong-Hyuk
aefc1292-87fd-48ab-94bc-a857692ccabe
Aspden, Andrew
7353e0e9-fbed-4f5a-a610-b045cd4cd576
Richardson, Edward
a8357516-e871-40d8-8a53-de7847aa2d08

Shin, Dong-Hyuk, Aspden, Andrew and Richardson, Edward (2017) Self-similar properties of decelerating turbulent jets. Journal of Fluid Mechanics, 833, R1. (doi:10.1017/jfm.2017.600).

Record type: Article

Abstract

The flow in a decelerating turbulent round jet is investigated using direct numerical simulation. The simulations are initialised with a flow field from a statistically-stationary turbulent jet. Upon stopping the inflow, a deceleration wave passes through the jet, behind which the velocity field evolves towards a new statistically-unsteady self-similar state. Assumption of unsteady self-similar behaviour leads to analytical relations concern-ing the evolution of the centreline mean axial velocity and the shapes of the radial profiles of the velocity statistics. Consistency between these predictions and the simulation data supports the use of the assumption of self-similarity. The mean radial velocity is predicted to reverse in direction near to the jet centreline as the deceleration wave passes, contributing to an approximately three-fold increase in the normalised mass entrainment rate. The shape of the mean axial velocity profile undergoes a relatively small change across the deceleration transient, and this observation provides direct evidence in support of previous models that have assumed that the mean axial velocity profile, and in some cases also the jet spreading angle, remain approximately constant within unsteady jets.

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Self_similar_properties_of_decelerating_turbulent_jets - Accepted Manuscript
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Accepted/In Press date: 20 August 2017
e-pub ahead of print date: 2 November 2017
Published date: 25 December 2017

Identifiers

Local EPrints ID: 412985
URI: http://eprints.soton.ac.uk/id/eprint/412985
ISSN: 0022-1120
PURE UUID: 3de9207d-3d1a-4efd-8e84-07f37022ba95

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Date deposited: 10 Aug 2017 16:30
Last modified: 30 Jan 2020 05:03

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