Imperial College London

ProfessorSpencerSherwin

Faculty of EngineeringDepartment of Aeronautics

Professor of Computational Fluid Mechanics
 
 
 
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Contact

 

+44 (0)20 7594 5052s.sherwin Website

 
 
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Location

 

313BCity and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Yakhot:2019:10.1007/s10494-018-0002-8,
author = {Yakhot, A and Feldman, Y and Moxey, D and Sherwin, S and Karniadakis, GE},
doi = {10.1007/s10494-018-0002-8},
journal = {Flow, Turbulence and Combustion},
title = {Turbulence in a Localized Puff in a Pipe},
url = {http://dx.doi.org/10.1007/s10494-018-0002-8},
year = {2019}
}

RIS format (EndNote, RefMan)

TY  - JOUR
AB - © 2019, Springer Nature B.V. We have performed direct numerical simulations of a spatio-temporally intermittent flow in a pipe for Rem = 2250. From previous experiments and simulations of pipe flow, this value has been estimated as a threshold when the average speeds of upstream and downstream fronts of a puff are identical (Barkley et al., Nature 526, 550–553, 2015; Barkley et al., 2015). We investigated the structure of an individual puff by considering three-dimensional snapshots over a long time period. To assimilate the velocity data, we applied a conditional sampling based on the location of the maximum energy of the transverse (turbulent) motion. Specifically, at each time instance, we followed a turbulent puff by a three-dimensional moving window centered at that location. We collected a snapshot-ensemble (10000 time instances, snapshots) of the velocity fields acquired over T = 2000D/U time interval inside the moving window. The cross-plane velocity field inside the puff showed the dynamics of a developing turbulence. In particular, the analysis of the cross-plane radial motion yielded the illustration of the production of turbulent kinetic energy directly from the mean flow. A snapshot-ensemble averaging over 10000 snapshots revealed azimuthally arranged large-scale (coherent) structures indicating near-wall sweep and ejection activity. The localized puff is about 15-17 pipe diameters long and the flow regime upstream of its upstream edge and downstream of its leading edge is almost laminar. In the near-wall region, despite the low Reynolds number, the turbulence statistics, in particular, the distribution of turbulence intensities, Reynolds shear stress, skewness and flatness factors, become similar to a fully-developed turbulent pipe flow in the vicinity of the puff upstream edge. In the puff core, the velocity profile becomes flat and logarithmic. It is shown that this “fully-developed turbulent flash” is very narrow being about t
AU - Yakhot,A
AU - Feldman,Y
AU - Moxey,D
AU - Sherwin,S
AU - Karniadakis,GE
DO - 10.1007/s10494-018-0002-8
PY - 2019///
SN - 1386-6184
TI - Turbulence in a Localized Puff in a Pipe
T2 - Flow, Turbulence and Combustion
UR - http://dx.doi.org/10.1007/s10494-018-0002-8
ER -