dc.contributor.author | Yakhot, A | |
dc.contributor.author | Feldman, Y | |
dc.contributor.author | Moxey, D | |
dc.contributor.author | Sherwin, S | |
dc.contributor.author | Karniadakis, G | |
dc.date.accessioned | 2019-01-15T10:34:52Z | |
dc.date.issued | 2019-01-12 | |
dc.description.abstract | 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 two pipe diameters long. | en_GB |
dc.identifier.citation | Published online 12 January 2019 | en_GB |
dc.identifier.doi | 10.1007/s10494-018-0002-8 | |
dc.identifier.uri | http://hdl.handle.net/10871/35459 | |
dc.language.iso | en | en_GB |
dc.publisher | Springer Verlag | en_GB |
dc.rights.embargoreason | Under embargo until 12 January 2020 in compliance with publisher policy | |
dc.rights | © 2018 Springer Verlag | en_GB |
dc.subject | Transition to turbulence | en_GB |
dc.subject | Puff | en_GB |
dc.subject | Pipe flow | en_GB |
dc.title | Turbulence in a localized puff in a pipe | en_GB |
dc.type | Article | en_GB |
dc.date.available | 2019-01-15T10:34:52Z | |
dc.identifier.issn | 0003-6994 | |
dc.description | This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record | en_GB |
dc.identifier.journal | Flow, Turbulence and Combustion | en_GB |
dc.rights.uri | http://www.rioxx.net/licenses/all-rights-reserved | en_GB |
dcterms.dateAccepted | 2018-12-04 | |
rioxxterms.version | AM | en_GB |
rioxxterms.licenseref.startdate | 2018-12-04 | |
rioxxterms.type | Journal Article/Review | en_GB |
refterms.dateFCD | 2019-01-14T10:38:05Z | |
refterms.versionFCD | AM | |
refterms.panel | B | en_GB |