A high-frequency surface heat flux imaging technique was used to investigate bypass transition induced by freestream turbulence. Fundamental experiments were carried out at the University of Oxford using high-density thin film arrays on a flat plate wind tunnel model. Bypass transition was induced by grid-generated turbulence with varying intensities of 2.3%, 4.2%, and 17% with a fixed integral length scale of approximately 12mm. Unique high resolution temporal heat flux images are shown which detail significant differences between unsteady surface heat flux events induced by freestream turbulence and the classical Emmons-type spots which many turbomachinery transition models are based on. The temporal imaging technique presented allows study of unsteady surface heat transfer in detail, and helps elucidate the complex nature of transition in the high-disturbance environment of turbomachinery.

1.
Dunn
,
M. G.
, 2001. “
Convective Heat Transfer and Aerodynamics in Axial Flow Turbines
,” ASME Paper No. 2001-GT-0506.
2.
Mayle
,
R. E.
, 1991. “
The Role of Laminar-Turbulent Transition in Gas Turbine Engines
,”
ASME J. Turbomach.
0889-504X,
113
, pp.
509
537
.
3.
Schlichting
,
H.
, 2000,
Boundary Layers
,
9th ed.
,
McGraw–Hill
, New York.
4.
White
,
F. M.
, 1974,
Viscous Fluid Flow
,
1st ed.
,
McGraw-Hill
, New York.
5.
Morkovin
,
M. V.
, 1993. “
Bypass—Transition Research: Issues and Philosophy
,”
Instabilities and Turbulence in Engineering Flows
, edited by
D. E.
Ashpis
,
T. B.
Gatski
,
R.
Hirsch
,
Kluwer Academic
, Dordrecht, 1993, pp.
3
30
.
6.
Abu Ghannam
,
B. J.
and
Shaw
,
R.
, 1980. “
Natural transition of boundary layers—the effects of turbulence, pressure gradient, and flow history
,”
J. Mech. Eng. Sci.
0022-2542,
22
, pp.
213
228
.
7.
Narasimha
,
R.
, 1985. “
The Laminar-Turbulent Transition Zone in the Boundary Layer
,”
Prog. Aerosp. Sci.
0376-0421,
22
, pp.
29
80
.
8.
Fraser
,
C. J.
,
Higazy
,
M. G.
, and
Milne
,
J. S.
, 1994. “
End-stage boundary layer transition models for engineering calculations
,”
Proc. Inst. Mech. Eng.
0020-3483, IMechE,
208
, pp.
47
60
.
9.
Emmons
,
H. W.
, 1951. “
The Laminar-Turbulent Transition in a Boundary Layer—Part 1
,”
J. Aeronaut. Sci.
0095-9812,
18
, pp.
490
498
.
10.
Kittichaikarn
,
C.
,
Ireland
,
P. T.
,
Zhong
,
S.
, and
Hodson
,
H. P.
, 1999. “
An investigation on the onset of wake-induced transition and turbulent spot production rate using thermochromic liquid crystals
,” ASME Paper No. 99-GT-126.
11.
Matsubara
,
M.
,
Alfredsson
,
P. H.
, and
Westin
,
K. J. A.
, 1998. “
Boundary layer transition at high levels of free stream turbulence
,” ASME Paper No. 98-GT-248.
12.
Jacobs
,
R. G.
,
Durbin
and
P. A.
, 2001. “
Simulations of bypass transition
,”
J. Fluid Mech.
0022-1120,
428
, pp.
185
212
.
13.
Kendall
,
J. M.
, 1985. “
Experimental study of disturbances produced in a pre-transitional laminar boundary layer by weak freestream turbulence
,” AIAA Paper No. 85-1695.
14.
Schmid
,
P. J.
,
Henningson
,
D. S.
, 2001, “
Stability and transition in shear flows
,”
Applied Mathematical Sciences
,
Springer-Verlag
, Berlin, Vol.
142
.
15.
Anthony
,
R. J.
,
Jones
,
T. V.
, and
LaGraff
,
J. E
, 2004. “
Unsteady surface heat flux under a three-dimensional crossflow boundary layer
,” AIAA Paper No. 2004-1344.
16.
Schultz
,
D. L.
and
Jones
,
T. V.
, 1973. “
Heat Transfer Measurements in Short-Duration Hypersonic Facilities
,” AGARD AG-165.
17.
Roach
,
P. E.
, 1987. “
The generation of nearly isotropic turbulence by means of grids
,”
Int. J. Heat Fluid Flow
0142-727X,
8
,(2)
82
18.
Wu
,
X.
,
Jacobs
,
R. G.
,
Hunt
,
J. C. R.
, and
Durbin
,
P. A.
, 1999. “
Simulation of boundary layer transition induced by periodically passing wakes
,”
J. Fluid Mech.
0022-1120,
398
, pp.
109
153
.
19.
Acarlar
,
M. S.
and
Smith
,
C. R.
, 1987. “
A study of hairpin vortices in a laminar boundary layer. Part 2. Hairpin vortices generated by fluid injection
,”
J. Fluid Mech.
0022-1120,
175
, pp.
43
83
.
20.
Wygnanski
,
I.
,
Haritonidis
,
J. E.
, and
Kaplan
,
R. E.
, 1979. “
On a Tollmien-Schlichting wave packet produced by a turbulent spot
,”
J. Fluid Mech.
0022-1120,
92
, p.
505
.
21.
Sankaran
,
R.
,
Sokolov
,
M.
, and
Antonia
,
R. A.
, 1988. “
Substructures in a turbulent spot
,”
J. Fluid Mech.
0022-1120,
197
, pp.
389
414
.
22.
Anthony
,
R. J.
,
Oldfield
,
M. L. G.
,
Jones
,
T. V.
, and
LaGraff
,
J. E
, 1999. “
Development of High Density Arrays of Thin Film Heat Transfer Gauges
,”
Proceedings of the 5th ASME/JSME Thermal Engineering Joint Conference
,
San Diego
, CA. Paper No. AJTE99-6159.
23.
Sabatino
,
D.
and
Smith
,
C. R.
, 2002. “
Simultaneous velocity-surface heat transfer behavior of turbulent spots
,”
Exp. Fluids
0723-4864,
33
, pp.
13
21
.
24.
Moss
,
R. W.
, 1992, “
The effects of turbulence length scale on heat transfer
,” Ph.D. Thesis, Department of Engineering Science, University of Oxford, Report No. OUEL 1924/92.
25.
Dullenkopf
,
K.
, and
Mayle
,
R. E.
, 1995. “
An account of free-stream-turbulence length scale on laminar heat transfer
,”
ASME J. Turbomach.
0889-504X,
117
, pp.
401
406
.
26.
Schook
,
R.
,
de Lange
,
H. C.
, and
van Steenhoven
,
A. A.
, 1998. “
Effects of compressibility and turbulence level on bypass transition
,” ASME Paper No. 98-GT-286.
27.
Morkovin
,
M. V.
, 1969. “
On the many faces of transition
,”
Viscous Drag Reduction
, edited by
C.
Wells
,
Plenum
, NY, pp.
1
31
.
28.
Coupland
,
J.
, 1995. “
Transition modelling for turbomachinery flows
,”
European Research Community On Flow Turbulence And Combustion (ERCOFTAC) Bulletin
, Iss. 24, March 1995, pp.
5
8
.
29.
Schubauer
,
G. B.
and
Klebanoff
,
P. S.
, 1955. “
Contributions on the Mechanics of Boundary Layer Transition
,” NASA TN-3489.
You do not currently have access to this content.