The effect of lateral conduction on convective heat transfer measurements using a transient infrared technique over an isolated spherical roughness element (bump) is evaluated. Comparisons are made between a full 3D finite-volume analysis and a simpler 1D transient conduction model. The surface temperature history was measured with a high resolution infrared camera during an impulsively started hot-gas flow at a flow Reynolds number of 860,000. The boundary layer was turbulent with the bump heights equivalent to 0.75, 1.5, and 3 times the boundary layer momentum thickness. When considering transient conduction effects only in the bump wake, the 1D approximate method underestimates the actual Stanton number estimated with the 3D model. This discrepancy is only 10% for a 75% change in St number occurring over a surface distance of 10 mm (the half-width of the wake). When the actual bump topology is accounted for in estimating the Stanton number on the bump itself with the 3D analysis technique, the increased surface area of the finite-volume cells on the protruding bump actually decreases the predicted value of St locally. The net result is that the two effects can cancel each other, and in some cases the 1D approximate technique can provide a reasonably accurate estimate of the surface heat transfer without the added complexity of the 3D finite-volume method. For the case of the largest bump tested, with maximum surface angularity exceeding 60 deg, the correction for 3D topology yields a 1D St estimate that is within 20–30% of the 3D estimate over much of the bump surface. These observed effects are valid for transient measurement techniques while the opposite is true for steady-state measurement techniques.

1.
Nikuradse
,
J.
, 1933, “
Laws for Flows in Rough Pipes
,”
VDI-Forchungsheft 361, Series B
, Vol.
4
(English Translation NACA, TM-1292, 1950).
2.
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
. 0022-0825
3.
Turner
,
A.
,
Tarada
,
F.
, and
Bayley
,
F.
, 1985, “
Effects of Surface Roughness on Heat Transfer to Gas Turbine Blades
,” Paper No. AGARD-CP-390, p.
9
.
4.
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
. 0742-4795
5.
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 Transfer
0017-9310,
40
(
12
), pp.
2813
2823
.
6.
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
. 0098-2202
7.
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 Transfer
0017-9310,
34
(
4/5
), pp.
1067
1082
.
8.
Henry
,
R. C.
,
Hansman
,
R. J.
, and
Breuer
,
K. S.
, 1995, “
Heat Transfer Variation on Protuberances and Surface Roughness Elements
,”
J. Thermophys. Heat Transfer
0887-8722,
9
(
1
), pp.
175
180
.
9.
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
. 0098-2202
10.
Bogard
,
D. G.
,
Schmidt
,
D. L.
, and
Tabbita
,
M.
, 1998, “
Characterization and Laboratory Simulation of Turbine Airfoil Surface Roughness and Associated Heat Transfer
,”
J. Turbomach.
0889-504X,
120
(
2
), pp.
337
342
.
11.
Barlow
,
D. N.
, and
Kim
,
Y. W.
, 1995, “
Effect of Surface Roughness on Local Heat Transfer and Film Cooling Effectiveness
,” presented at the
ASME International Gas Turbine Exposition in Houston
, Houston, Texas, Jun., ASME, Paper No. 95-GT-14.
12.
Bons
,
J. P.
, 2009, “
Transient Method for Convective Heat Transfer Measurement With Lateral Conduction—Part I: Application to a Deposit-Roughened Gas Turbine Surface
,”
ASME J. Heat Transfer
0022-1481,
131
(
1
), p.
011301
.
13.
McClain
,
S. T.
,
Vargas
,
M.
,
Kreeger
,
R. E.
, and
Tsao
,
J.-C.
, 2007, “
Heat Transfer From Protuberances
,”
J. Thermophys. Heat Transfer
0887-8722,
21
(
2
), pp.
337
345
.
14.
Coleman
,
H. W.
,
Moffat
,
R. J.
, and
Kays
,
W. M.
, 1981, “
Heat Transfer in the Accelerated Fully Rough Turbulent Boundary Layer
,”
ASME J. Heat Transfer
,
103
, pp.
153
158
. 0022-1481
15.
Sabatino
,
D. R.
, and
Smith
,
C. R.
, 2007, “
Boundary Layer Influence on the Unsteady Horseshoe Vortex Flow and Surface Heat Transfer
,” ASME Paper No. GT2007-27633.
16.
Waye
,
S. K.
, and
Bogard
,
D. G.
, 2007, “
High-Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations
,”
ASME J. Turbomach.
0889-504X,
129
, pp.
294
302
.
You do not currently have access to this content.