Research Papers

Numerical Study of Turbulent-Spot Development in a Separated Shear Layer

[+] Author and Article Information
Brian R. McAuliffe1

Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canadabrian.mcauliffe@nrc-cnrc.gc.ca

Metin I. Yaras

Department of Mechanical and Aerospace Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canadametiṉyaras@carleton.ca


Present address: Aerodynamics Laboratory, Institute for Aerospace Research, National Research Council of Canada, 1200 Montreal Road, Building M-2, Ottawa, ON, K1A 0R6, Canada.

J. Turbomach 130(4), 041018 (Aug 04, 2008) (9 pages) doi:10.1115/1.2812948 History: Received June 12, 2007; Revised August 03, 2007; Published August 04, 2008

The development of turbulent spots in a separation bubble under elevated freestream turbulence levels is examined through direct numerical simulation. The flow Reynolds number, freestream turbulence level, and streamwise pressure distribution are typical of the conditions encountered on the suction side of low-pressure turbine blades of gas-turbine engines. Based on the simulation results, the spreading and propagation rates of the turbulent spots and their internal structure are documented, and comparisons are made to empirical correlations that are used for predicting the transverse growth and streamwise propagation characteristics of turbulent spots. The internal structure of the spots is identified as a series of vortex loops that develop as a result of low-velocity streaks generated in the shear layer. A frequency that is approximately 50% higher than that of the Kelvin–Helmholtz instability is identified in the separated shear layer, which is shown to be associated with the convection of these vortex loops through the separated shear layer. While freestream turbulence is noted to promote breakdown of the laminar separated shear layer into turbulence through the generation of turbulent spots, evidence is found to suggest coexistence of the Kelvin–Helmholtz instability, including the possibility of breakdown to turbulence through this mechanism.

Copyright © 2008 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

Schematic of computational domain

Grahic Jump Location
Figure 2

Streamwise distributions of freestream velocity and turbulence intensity

Grahic Jump Location
Figure 3

Comparison of simulated and measured velocity time traces with an intermittency of 0.5 (experimental data from a test case of Roberts and Yaras(2))

Grahic Jump Location
Figure 4

Velocity profiles, intermittency distribution, and spot origin histogram through the bubble region

Grahic Jump Location
Figure 5

Unsteadiness of separation location: (a) z-x near-wall plane and (b) z-y plane at the averaged separation location

Grahic Jump Location
Figure 6

Vortex loops within a turbulent spot

Grahic Jump Location
Figure 7

Turbulent-spot growth as observed in the y-t and z-t planes

Grahic Jump Location
Figure 8

Schematic of vortex loop structure during the early development of a turbulent spot

Grahic Jump Location
Figure 9

Power spectra of (a) velocity and (b) static pressure

Grahic Jump Location
Figure 10

Spot spreading half angles

Grahic Jump Location
Figure 11

Identification of spot celerities: (a) leading edge and (b) trailing edge



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In