An artificial turbulent spot is simulated in a zero free-stream turbulence base flow and a base flow with organized streaks. Six identification methods are used in order to isolate the turbulent spot from the surrounding nonturbulent fluid. These are (i) instantaneous wall-normal velocity v, (ii) instantaneous spanwise velocity w, (iii) instantaneous turbulent dissipation, (iv) λ2 criterion, (v) Q criterion, and (vi) gradient of the finite time Lyapunov exponent. All methods are effective in isolating the turbulent spot from the streaks. The robustness of each technique is determined from the sensitivity of the maximum spot dimensions to changes in threshold level. The Q criterion shows the least sensitivity for the zero free-stream turbulence case and the instantaneous turbulent dissipation technique is least sensitive in the organized streaks case. For both cases the v technique was the most sensitive to changes in threshold level.

References

References
1.
Walsh
,
E. J.
, and
Davies
,
M. R. D.
,
2004
, “
Measurements in the Transition Region of a Turbine Blade Profile Under Compressible Conditions
,”
ASME J. Fluids Eng.
,
127
, pp.
400
403
.10.1115/1.1881699
2.
Zaki
,
T. A.
,
Wissink
,
J.
,
Rodi
,
W.
, and
Durbin
,
P. A.
,
2010
, “
DNS of Transition in a Compressor Cascade: The Influence of Free-Stream Turbulence
,”
J. Fluid Mech.
,
665
, pp.
57
98
.10.1017/S0022112010003873
3.
Zaki
,
T. A.
,
Wissink
,
J.
,
Durbin
,
P. A.
, and
Rodi
,
W.
,
2009
, “
Direct Computations of Boundary Layers Distorted by Migrating Wakes in a Linear Compressor Cascade
,”
Flow Turb. Combust.
,
83
(
3
), pp.
307
322
.10.1007/s10494-009-9216-0
4.
Emmons
,
H. W.
,
1951
, “
The Laminar-Turbulent Transition in a Boundary Layer
,”
J. Aero. Sci.
,
18
, pp.
490
498
.
5.
Schlichting
,
H.
,
1979
,
Boundary Layer Theory
,
McGraw Hill
,
New York
.
6.
Jacobs
,
R. G.
, and
Durbin
,
P. A.
,
2001
, “
Simulations of Bypass Transition
,”
J. Fluid Mech.
,
428
, pp.
185
212
.10.1017/S0022112000002469
7.
Zaki
,
T. A.
, and
Saha
,
S.
,
2009
. “
On Shear Sheltering and the Structure of Vortical Modes in Single and Two-Fluid Boundary Layers
,”
J. Fluid Mech.
,
626
, pp.
111
147
.10.1017/S0022112008005648
8.
Zaki
,
T. A.
, and
Durbin
,
P. A.
,
2005
, “
Mode Interaction and the Bypass Route to Transition
,”
J. Fluid Mech.
,
531
, pp.
85
111
.10.1017/S0022112005003800
9.
Schubauer
,
G. B.
, and
Klebanoff
,
P. S.
,
1955
,
Contributions on the Mechanics of Boundary Layer Transition
, Tech. Note TN 3489, NACA.
10.
Gad-el-hak
,
M.
,
Blackwelder
,
R. F.
, and
Riley
,
J. J.
,
1981
, “
On the Growth of Turbulent Regions in Laminar Boundary-Layers
,”
J. Fluid Mech.
,
110
, pp.
73
95
.10.1017/S002211208100061X
11.
Sankaran
,
R.
,
Sokolov
,
M.
, and
Antonia
,
R. A.
,
1988
, “
Substructures in a Turbulent Spot
,”
J. Fluid Mech.
,
197
, pp.
389
414
.10.1017/S0022112088003295
12.
Singer
,
B. A.
,
1996
, “
Characteristics of a Young Turbulent Spot
,”
Phys. Fluids
,
8
(
2
), pp.
509
521
.10.1063/1.868804
13.
Ching
,
C. Y.
, and
LaGraff
,
J. E.
,
1995
, “
Measurement of Turbulent Spot Convection Rates in a Transitional Boundary Layer
,”
Exp. Thermal Fluid Sci.
,
11
, pp.
52
60
.10.1016/0894-1777(94)00111-K
14.
Jocksch
,
A.
, and
Kleiser
,
L.
,
2008
, “
Growth of Turbulent Spots in High-Speed Boundary Layers on a Flat Plate
,”
IJHFF
,
29
(
6
), pp.
1542
1557
. 10.1016/j.ijheatfluidflow.2008.08.008
15.
Green
,
M. A.
,
Rowley
,
C. W.
, and
Haller
,
G.
,
2007
, “
Detection of Lagragian Coherent Structures in 3D Turbulence
,”
J. Fluid Mech.
,
572
, pp.
111
120
.10.1017/S0022112006003648
16.
Volino
,
R. J.
,
Schultz
,
M. P.
, and
Pratt
,
C. M.
,
2003
, “
Conditional Sampling in a Transitional Boundary Layer Under High Free-Stream Turbulence Conditions
,”
J. Fluids Eng.
,
125
, pp.
405
416
.10.1115/1.1521957
17.
Rehill
,
B.
,
Walsh
,
E. J.
,
Nolan
,
K.
,
McEligot
,
D. M.
,
Brandt
,
L.
,
Schlatter
,
P.
, and
Henningson
,
D. S.
,
2009
, “
Entropy Generation Rate in Turbulent Spots in a Boundary Layer Subject to Freestream Turbulence
,”
Proceedings of the Seventh IUTAM Symposium on Laminar-Turbulent Transition
, Vol.
18
,
Springer
,
Berlin
, pp.
557
560
.
18.
Gutmark
,
E.
, and
Blackwelder
,
R. F.
,
1987
, “
On the Structure of a Turbulent Spot in a Heated Laminar Boundary Layer
,”
Exp. Fluids
,
5
, pp.
217
222
. 10.1007/BF00279733
19.
Levin
,
O.
, and
Henningson
,
D. S.
,
2007
, “
Turbulent Spots in the Asymptotic Suction Boundary Layer
,”
J. Fluid Mech.
,
584
, pp.
397
413
.10.1017/S0022112007006544
20.
Brandt
,
L.
,
Schlatter
,
P.
, and
Henningson
,
D. S.
,
2004
, “
Transition in Boundary Layers Subject to Freestream Turbulence
,”
J. Fluid Mech.
,
517
, pp.
167
198
.10.1017/S0022112004000941
21.
Hernon
,
D.
, and
Walsh
,
E. J.
,
2007
, “
Enhanced Energy Dissipation Rates in Laminar Boundary Layers Subjected to Elevated Levels of Freestream Turbulence
,”
Fluid Dyn. Res.
,
39
(
4
), pp.
305
319
.10.1016/j.fluiddyn.2006.07.001
22.
Nolan
,
K. P.
,
Walsh
,
E. J.
, and
McEligot
,
D. M.
,
2010
, “
Quadrant Analysis of a Transitional Boundary Layer Subject to Free-Stream Turbulence
,”
J. Fluid Mech.
,
658
, pp.
310
335
.10.1017/S0022112010001758
23.
Hunt
,
J. C. R.
,
Wray
,
A. A.
, and
Moin
,
P.
,
1988
, “
Eddies, Stream, and Convergence Zones in Turbulent Flows
,”
Center for Turbulence Research Rep. CTR-S88
.
24.
Jeong
,
J.
, and
Hussein
,
F.
,
1995
, “
On the Identification of a Vortex
,”
J. Fluid Mech.
,
285
, pp.
69
94
.10.1017/S0022112095000462
25.
Haller
,
G.
,
2002
, “
Lagrangian Coherent Structures From Approximate Velocity Data
,”
Phys. Fluids
,
14
(
6
), pp.
1851
1861
.10.1063/1.1477449
26.
Seifert
,
A.
,
Zilberman
,
M.
, and
Wygnanski
,
I.
,
1994
, “
On the Simultaneous Measurements of Two Velocity Components in the Turbulent Spot
,”
J. Eng. Math.
,
28
, pp.
43
54
.10.1007/BF02383604
27.
Schroder
,
A.
, and
Kompenhans
,
J.
,
2004
, “
Investigation of a Turbulent Spot Using Multi-Plane Stereo Particle Image Velocimety
,”
Exp. Fluids
,
36
, pp.
82
90
.10.1007/s00348-003-0644-7
28.
Matsubara
,
M.
, and
Alfredsson
,
P. H.
,
2001
, “
Disturbance Growth in Boundary Layers Subjected to Free-Stream Turbulence
,”
J. Fluid Mech.
,
430
, pp.
149
168
.10.1017/S0022112000002810
29.
Denton
,
J. D.
,
1993
, “
Loss Mechanisms in Turbomachines
,”
ASME J. Turbomach.
,
115
, pp.
621
657
.10.1115/1.2929299
You do not currently have access to this content.