Experimental measurements of skin friction cf and heat transfer (St) augmentation are reported for low speed flow over turbine roughness models. The models were scaled from surface measurements taken on actual, in-service land-based turbine hardware. Model scaling factors ranged from 25 to 63, preserving the roughness height to boundary layer momentum thickness ratio for each case. The roughness models include samples of deposits, TBC spallation, erosion, and pitting. Measurements were made in a zero pressure gradient turbulent boundary layer at two Reynolds numbers (Rex=500,000 and 900,000) and three freestream turbulence levels (Tu=1%, 5%, and 11%). Measurements at low freestream turbulence indicate augmentation factors ranging from 1.1–1.5 for St/Sto and from 1.3–3.0 for cf/cfo(Sto and cfo are smooth plate values). For the range of roughness studied (average roughness height, k, less than 1/3rd the boundary layer thickness) the level of cf augmentation agrees well with accepted equivalent sandgrain ks correlations when ks is determined from a roughness shape/density parameter. This finding is not repeated with heat transfer, in which case the ks-based St correlations overpredict the measurements. Both cf and St correlations severely underpredict the effect of roughness for k+<70 (when ks, as determined by the roughness shape/density parameter, is small). A new ks correlation based on the rms surface slope angle overcomes this limitation. Comparison of data from real roughness and simulated (ordered cones or hemispheres) roughness suggests that simulated roughness is fundamentally different from real roughness. Specifically, ks values that correlate cf for both simulated and real roughness are found to correlate St for simulated roughness but overpredict St for real roughness. These findings expose limitations in the traditional equivalent sandgrain roughness model and the common use of ordered arrays of roughness elements to simulate real roughness surfaces. The elevated freestream turbulence levels produce augmentation ratios of 1.24 and 1.5 St/Sto and 1.07 and 1.16 cf/cfo compared to the Tu=1% flow over the smooth reference plate. The combined effects of roughness and elevated freestream turbulence are greater than their added effects suggesting that some synergy occurs between the two mechanisms. Specifically, skin friction augmentation for combined turbulence and roughness is up to 20% greater than that estimated by adding their separate effects and 8% greater than compounding (multiplying) their separate effects. For heat transfer augmentation, the combined effect of turbulence and roughness is 5% higher than that estimated by compounding their separate effects at high freestream turbulence (Tu=11%). At low turbulence (Tu=5%), there is a negative synergy between the two augmentation mechanisms as the combined effect is now 13% lower than that estimated by compounding their separate effects.

1.
Bons
,
J. P.
,
Taylor
,
R.
,
McClain
,
S.
, and
Rivir
,
R. B.
,
2001
, “
The Many Faces of Turbine Surface Roughness
,”
ASME J. Turbomach.
,
23
, pp.
739
748
.
2.
Acharya
,
M.
,
Bornstein
,
J.
, and
Escudier
,
M.
,
1986
, “
Turbulent Boundary Layers on Rough Surfaces
,”
Exp. Fluids
, No. 4, pp.
33
47
.
3.
Taylor
,
R. P.
,
1990
, “
Surface Roughness Measurements on Gas Turbine Blades
,”
ASME J. Turbomach.
,
112
(
1
), pp.
175
180
.
4.
Tarada, F., and Suzuki, M., 1993, “External Heat Transfer Enhancement to Turbine Blading due to Surface Roughness,” ASME Paper 93-GT-74.
5.
Blair
,
M. F.
,
1994
, “
An Experimental Study of Heat Transfer in a Large-Scale Turbine Rotor Passage
,”
ASME J. Turbomach.
,
116
(
1
), pp.
1
13
.
6.
Guo
,
S. M.
,
Jones
,
T. V.
,
Lock
,
G. D.
, and
Dancer
,
S. N.
,
1998
, “
Computational Prediction of Heat Transfer to Gas Turbine Nozzle Guide Vanes with Roughened Surfaces
,”
ASME J. Turbomach.
,
120
(
2
), pp.
343
350
.
7.
Boynton
,
J. L.
,
Tabibzadeh
,
R.
, and
Hudson
,
S. T.
,
1993
, “
Investigation of Rotor Blade Roughness Effects on Turbine Performance
,”
ASME J. Turbomach.
,
115
, pp.
614
620
.
8.
Suder
,
K. L.
,
Chima
,
R. V.
,
Strazisar
,
A. J.
, and
Roberts
,
W. B.
,
1995
, “
The Effect of Adding Roughness and Thickness to a Transonic Axial Compressor Rotor
,”
ASME J. Turbomach.
,
117
, pp.
491
505
.
9.
Ghenaiet, A., Elder, R. L., and Tan, S. C., “Particles Trajectories through an Axial Fan and Performance Degradation due to Sand Ingestion,” ASME Paper No. 2001-GT-497.
10.
Bammert
,
K.
, and
Sandstede
,
H.
,
1980
, “
Measurements of the Boundary Layer Development along a Turbine Blade with Rough Surfaces
,”
ASME J. Eng. Power
,
102
, pp.
978
983
.
11.
Turner, A., Tarada, F., and Bayley, F., 1985, “Effects of Surface Roughness on Heat Transfer to Gas Turbine Blades,” AGARD-CP-390, pp. 9-1 to 9-9.
12.
Hoffs, A., Drost, U., and Boles, A., 1996, “Heat Transfer Measurements on a Turbine Airfoil at Various Reynolds Numbers and Turbulence Intensities Including Effects of Surface Roughness,” presented at ASME IGTI in Birmingham, U.K., June 1996, ASME Paper No. 96-GT-169.
13.
Abuaf
,
N.
,
Bunker
,
R. S.
, and
Lee
,
C. P.
,
1998
, “
Effects of Surface Roughness on Heat Transfer and Aerodynamic Performance of Turbine Airfoils
,”
ASME J. Turbomach.
,
120
(
3
), pp.
522
529
.
14.
Pinson
,
M. W.
, and
Wang
,
T.
,
2000
, “
Effect of Two-Scale Roughness on Boundary Layer Transition over a Heated Flat Plate: Part 1 — Surface Heat Transfer
,”
ASME J. Turbomach.
,
122
(
2
), pp.
301
307
.
15.
Goldstein
,
R.
,
Eckert
,
E.
,
Chiang
,
H.
, and
Elovic
,
E.
,
1985
, “
Effect of Surface Roughness on Film Cooling Performance
,”
ASME J. Eng. Gas Turbines Power
,
107
, pp.
111
116
.
16.
Pinson
,
M. W.
, and
Wang
,
T.
,
1997
, “
Effects of Leading Edge Roughness on Fluid Flow and Heat Transfer in the Transitional Boundary Layer over a Flat Plate
,”
Int. J. Heat Mass Transf.
,
40
(
12
), pp.
2813
2823
.
17.
Taylor
,
R. P.
,
Scaggs
,
W. F.
, and
Coleman
,
H. W.
,
1988
, “
Measurement and Prediction of the Effects of Nonuniform Surface Roughness on Turbulent Flow Friction Coefficients
,”
ASME J. Fluids Eng.
,
110
, pp.
380
384
.
18.
Hosni
,
M. H.
,
Coleman
,
H. W.
, and
Taylor
,
R. P.
,
1991
, “
Measurements and Calculations of Rough-Wall Heat Transfer in the Turbulent Boundary Layer
,”
Int. J. Heat Mass Transf.
34
(
4/5
), pp.
1067
1082
.
19.
Scaggs
,
W. F.
,
Taylor
,
R. P.
, and
Coleman
,
H. W.
,
1988
, “
Measurement and Prediction of Rough Wall Effects on Friction Factor — Uniform Roughness Results
,”
ASME J. Fluids Eng.
,
110
, pp.
385
391
.
20.
Bogard
,
D. G.
,
Schmidt
,
D. L.
, and
Tabbita
,
M.
,
1998
, “
Characterization and Laboratory Simulation of Turbine Airfoil Surface Roughness and Associated Heat Transfer
,”
ASME J. Turbomach.
,
120
(
2
), pp.
337
342
.
21.
Barlow, D. N., and Kim, Y. W., 1995, “Effect of Surface Roughness on Local Heat Transfer and Film Cooling Effectiveness,” ASME Paper No. 95- GT-14.
22.
Kithcart, M. E., and Klett, D. E., 1997, “Heat Transfer and Skin Friction Comparison of Dimpled Versus Protrusion Roughness,” NASA N97-27444, pp. 328–336.
23.
Sigal
,
A.
, and
Danberg
,
J.
,
1990
, “
New Correlation of Roughness Density Effect on the Turbulent Boundary Layer
,”
AIAA J.
,
28
(
3
), pp.
554
556
.
24.
Nikuradse, J., 1933, “Laws for Flows in Rough Pipes,” VDI-Forchungsheft 361, Series B, Vol. 4. (English trans. NACA TM 1292, 1950).
25.
Antonia
,
R. A.
, and
Luxton
,
R. E.
,
1971
, “
The Response of a Turbulent Boundary Layer to a Step Change in Surface Roughness. Part 1: Smooth to Rough
,”
J. Fluid Mech.
48
, pp.
721
726
.
26.
Taylor, R. P., and Chakroun, W. M., 1992, “Heat Transfer in the Turbulent Boundary Layer with a Short Strip of Surface Roughness,” AIAA Paper No. 92-0249.
27.
Schultz, D. L., and Jones, T. V., 1973, “Heat-transfer Measurements in Short-duration Hypersonic Facilities,” Advisory Group for Aerospace Research and Development, No. 165, NATO.
28.
Drab, J. W., and Bons, J. P., 2002, “Turbine Blade Surface Roughness Effects on Shear Drag and Heat Transfer,” AIAA Paper No. 2002-0085.
29.
Mills, A. F., Heat Transfer, 1st Edition, 1992, Irwin, IL.
30.
White, F. M., Viscous Fluid Flow, 2nd Edition, 1991, McGraw-Hill, New York, NY.
31.
Kays, W. M., and Crawford, M. E., Convective Heat and Mass Transfer, 3rd Edition, 1993, McGraw-Hill, New York, NY.
32.
Schlichting, H., Boundary Layer Theory, 7th Edition, 1979, McGraw-Hill, New York, NY.
33.
Dipprey
,
D. F.
, and
Sabersky
,
R. H.
,
1963
, “
Heat and Momentum Transfer in Smooth and Rough Tubes at Various Prandtl Numbers
,”
Int. J. Heat Mass Transfer
,
6
, pp.
329
353
.
34.
Wassel
,
A. T.
, and
Mills
,
A. F.
,
1979
, “
Calculation of Variable Property Turbulent Friction and Heat Transfer in Rough Pipes
,”
ASME J. Heat Transfer
,
101
, pp.
469
474
.
35.
Mahmood, G. I., Hill, M. L., Nelson, D. L. Ligrani, P. M., Moon, H.-K., and Glezer, B., 2000, “Local Heat Transfer and Flow Structure on and Above a Dimpled Surface in a Channel,” ASME Paper No. 2000-GT-230 presented at ASME TURBOEXPO, Munich, Germany, May.
36.
Pinson
,
M. W.
, and
Wang
,
T.
,
2000
, “
Effect of Two-Scale Roughness on Boundary Layer Transition over a Heated Flat Plate: Part 1 — Surface Heat Transfer
,”
ASME J. Turbomach.
,
122
, pp.
301
307
.
37.
Pedisius
,
A. A.
,
Kazimekas
,
V. A.
, and
Slanciauskas
,
A. A.
,
1979
, “
Heat Transfer from a Plate to a High-Turbulence Air Flow
,”
Soviet Research
11
, pp.
125
134
.
38.
Maciejewski
,
P. K.
, and
Moffat
,
R. J.
,
1992
, “
Heat Transfer with Very High Free-Stream Turbulence: Part 1 — Experimental Data
,”
ASME J. Heat Transfer
,
114
, pp.
827
833
.
39.
Blair
,
M. F.
,
1983
, “
Influence of Free-Stream Turbulence on Turbulent Boundary Layer Heat Transfer and Mean Profile Development: Part II — Analysis of Results
,”
ASME J. Heat Transfer
,
105
, pp.
41
47
.
40.
Baskaran, V., Abdellatif, O. E, and Bradshaw, P., 1989, “Effects of Free-Stream Turbulence on Turbulent Boundary Layers with Convective Heat Transfer,” presented at the 7th Symposium on Turbulent Shear Flows, Stanford Univ., CA, Aug.
41.
Simonich
,
J. C.
, and
Bradshaw
,
P.
,
1978
, “
Effect of Free-Stream Turbulence on Heat Transfer Through a Turbulent Boundary Layer
,”
ASME J. Heat Transfer
,
100
, pp.
671
677
.
42.
Thole
,
K. A.
, and
Bogard
,
D. G.
,
1985
, “
Enhanced Heat Transfer and Shear Stress due to High Free-Stream Turbulence
,”
ASME J. Turbomach.
,
117
, pp.
418
424
.
43.
Sahm, M. K., and Moffat, R. J., 1992, “Turbulent Boundary Layers with High Turbulence: Experimental Heat Transfer and Structure on Flat and Convex Walls,” Stanford University Report HMT-45.
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