A highly loaded compressor cascade, which features a chord length ten times larger than in real turbomachinery, is used to perform an investigation of the influence of technical surface roughness. The surface structure of a precision forged blade was engraved in two 0.3-mm-thick sheets of copper with the above-mentioned enlarging factor (Leipold and Fottner, 1996). To avoid additional effects due to thickening of the blade contour, the sheets of copper are applied as inlays to the pressure and suction side. At the high-speed cascade wind tunnel, the profile pressure distribution and the total pressure distribution at the exit measurement plane were measured for the rough and the smooth blade for a variation of inlet flow angle and inlet Reynolds number. For some interesting flow conditions, the boundary layer development was investigated with laser-two-focus anemometry and one-dimensional hot-wire anemometry. At low Reynolds numbers and small inlet angles, a separation bubble is only slightly reduced due to surface roughness. The positive effect of a reduced separation bubble is overcompensated by a negative influence of surface roughness on the turbulent boundary layer downstream of the separation bubble. At high Reynolds numbers, the flow over the rough blade shows a turbulent separation leading to high total pressure loss coefficients. The laser-two-focus measurements indicate a velocity deficit close to the trailing edge, even at flow conditions where positive effects due to a reduction of the suction side separation have been expected. The turbulence intensity is reduced close downstream of the separation bubble but increased further downstream due to surface roughness. Thus the rear part of the blade but not the front part reacts sensitively on surface roughness. [S0889-504X(00)01302-7]

1.
Nikuradse, J., 1933, “Stro¨mungsgesetze in rauhen Rohren,” Beilage zu Forschung auf dem Gebiet des Ingenieurwesens, Forschungsheft 361 Ausgabe B Band 4.
2.
Schlichting, H., 1936, “Experimentelle Untersuchungen zum Rauhigkeitsproblem,” Ingenieur-Archiv 7. Band, 1. Heft.
3.
Bammert, K., and Sandstede, H., 1973, “Stro¨mungsverluste durch die Oberfla¨chenrauhigkeit der Schaufeln einer Turbine,” VDI-Berichte, No. 193.
4.
Bammert, K., and Sandstede, H., 1972, “Measurements Concerning the Influence of Surface Roughness and Profile Changes on the Performance of Gas Turbines,” ASME Paper No. 72-GT-34.
5.
Bammert, K., and Sandstede, H., 1975, “Influences of Manufacturing Tolerances and Surface Roughness of Blades on the Performance of Turbines,” ASME Paper No. 75-GT-35.
6.
Bammert, K., and Woelk, G.-U., 1976, “Der Einfluß der Profilrauhigkeit auf die Stro¨mungsverluste von Axialverdichtern,” VDI-Berichte No. 264.
7.
Bammert, K., and Woelk, G.-U., 1979, “The Influence of Blading Surface Roughness on the Aerodynamic Behavior and Characteristic of an Axial Compressor,” ASME Paper No. 79-GT-102.
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.
Bammert
,
K.
, and
Sandstede
,
H.
,
1980
, “
Measurements of the Boundary Layer Development Along a Turbine Blade With Rough Surfaces
,”
ASME J. Eng. Power
,
102
, No.
4
, pp.
978
983
.
10.
Bammert, K., and Milsch, R., 1972, “Das Verhalten der Grenzschicht an rauhen Verdichterschaufeln,” Sonderdruck Forschung im Ingenieurwesen, B. 38 No. 4.
11.
Saxena, V. M., Shirvastava, K. D., and Agrawal, P. K., 1980, “Effect of Surface Roughness Over the Blade in Compressor Cascade,” IE (I) 61.
12.
Sturm, W., and Fottner, L., 1985, “The High Speed Cascade Wind Tunnel of the German Armed Forces University Munich,” 8th Symposium on Measuring Techniques for Transonic and Supersonic Flows in Cascades and Turbomachines, Genoa.
13.
Leipold, R., and Fottner, L., 1998, “A Measurement Technique to Investigate the Influence of Surface Roughness on the Flow Around a Highly Loaded Compressor Cascade,” 14th Symposium on Measuring Techniques in Transonic and Supersonic Flow in Cascades and Turbomachines, Limerick.
14.
Hu¨bner, J., 1996, “Experimentelle und theoretische Untersuchung der wesentlichen Einflußfaktoren auf die Spalt- und Sekunda¨rstro¨mung in Verdichtergittern,” PhD Thesis, Universita¨t der Bundeswehr Mu¨nchen.
15.
Schodl, R., 1978, “Entwicklung des Laser-Zwei-Fokus-Verfahrens fu¨r die beru¨hrungslose Messung der Stro¨mungsvektoren, insbesondere in Turbomaschinen,” Ph.D. Thesis, Technische Hochschule Aachen.
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