University of Surrey

Test tubes in the lab Research in the ATI Dance Research

Turbulence in intermittent transitional boundary layers and in turbulence spots

Marxen, Olaf and Zaki, Tamer A. (2019) Turbulence in intermittent transitional boundary layers and in turbulence spots Journal of Fluid Mechanics, 860. pp. 350-383.

[img] Text
turbulence_in_intermittent_transitional_boundary_layers_and_in_turbulence_spots.pdf - Version of Record
Restricted to Repository staff only

Download (1MB)

Abstract

Direct numerical simulation data of bypass transition in flat-plate boundary layers are analysed to examine the characteristics of turbulence in the transitional regime. When intermittency is 50 % or less, the flow features a juxtaposition of turbulence spots surrounded by streaky laminar regions. Conditionally averaged turbulence statistics are evaluated within the spots, and are compared to standard time averaging in both the transition region and in fully turbulent boundary layers. The turbulent-conditioned root-mean-square levels of the streamwise velocity perturbations are notably elevated in the early transitional boundary layer, while the wall-normal and spanwise components are closer to the levels typical for fully turbulent flow. The analysis is also extended to include ensemble averaging of the spots. When the patches of turbulence are sufficiently large, they develop a core region with similar statistics to fully turbulent boundary layers. Within the tip and the wings of the spots, however, the Reynolds stresses and terms in the turbulence kinetic energy budget are elevated. The enhanced turbulence production in the transition zone, which exceeds the levels from fully turbulent boundary layers, contributes to the higher skin-friction coefficient in that region. Qualitatively, the same observations hold for different spot sizes and levels of free-stream turbulence, except for young spots which do not yet have a core region of developed turbulence.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Mechanical Engineering Sciences
Authors :
NameEmailORCID
Marxen, Olafo.marxen@surrey.ac.uk
Zaki, Tamer A.
Date : 10 February 2019
DOI : 10.1017/jfm.2018.822
Copyright Disclaimer : © 2018 Cambridge University Press
Uncontrolled Keywords : Boundary layers; Intermittency; Transition to turbulence
Depositing User : Clive Harris
Date Deposited : 14 Aug 2019 08:07
Last Modified : 14 Aug 2019 08:07
URI: http://epubs.surrey.ac.uk/id/eprint/852405

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year


Information about this web site

© The University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
+44 (0)1483 300800