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Wake Related Wind Tunnel Corrections for Closed Wall Test Sections
Technical Paper
2006-01-0567
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
In closed wall test sections the total correction to the measured drag usually consists of several parts: solid blockage corrections related to the displacement of the model, horizontal buoyancy corrections due to empty tunnel gradients and the wake blockage corrections, which are necessary to handle effects created by the displacement effect of the wake. The latter will be investigated in more detail in the paper.
The wake blockage correction usually consists of two parts: a correction to the measured dynamic pressure (q-correction) and a gradient correction, the so-called wake induced drag increment. Both corrections are directly dependent on the source strength which is equivalent to the displacement effect of the wake. Therefore the displacement of the wake is analyzed in more detail. It will be shown by using analytical as well as CFD results that the usual assumption of a displacement thickness equal to the momentum thickness introduces a significant error which results in severe undercorrection in high blockage conditions. This error affects both q-correction and wake induced drag increment, if the wake displacement is not determined from measured wall signatures (pressure, velocity).
It will be shown that the displacement effect of the wake is typically not constant but is dependent on the stream-wise distance from the model. The increase in displacement will be calculated for a number of cases, including streamlined and bluff bodies as well as laminar and turbulent flow in the wake. In order to keep an easily usable approximation for the wake displacement a proposal for an enhancement factor to the momentum thickness (which in the classical approach is used as approximation to the displacement) will be made.
Finally the total correction is tested using CFD results. Using the detailed flow information available from the numerical solutions the total correction is split up into the individual contributions of solid blockage, wake blockage and wake induced drag increment. It is found that the solid blockage correction and the wake induced drag increment are approximately correct, whereas the wake blockage contribution is still significantly too small. Possible reasons for this are discussed.
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Citation
Wickern, G., "Wake Related Wind Tunnel Corrections for Closed Wall Test Sections," SAE Technical Paper 2006-01-0567, 2006, https://doi.org/10.4271/2006-01-0567.Also In
SAE 2006 Transactions Journal of Passenger Cars: Mechanical Systems
Number: V115-6; Published: 2007-03-30
Number: V115-6; Published: 2007-03-30
References
- GLAUERT, H. Wind tunnel interference on wings, bodies and airscrews ARC, R.&M. 1566 1933
- BARLOW, J.B. RAE, W.H. POPE, A. Low-Speed Wind Tunnel Testing John Wiley & Sons New York 1999
- PANKHURST, R. C. HOLDER, D. W. Wind tunnel technique Pitman London 1965
- GARNER, H. C. Subsonic wind tunnel wall corrections AGARDograph 109 1966
- EWALD, B. Wind tunnel wall corrections AGARDograph 336 1998
- COOPER, K.R. Closed-test-section wind tunnel blockage corrections for road vehicles SAE SP-1176, Warrendale 1996
- PRANDTL, L. TIETJENS, O.G. Applied Hydro- and Aro-Mechanics V Engineering Society Monographs McGraw-Hill 1934
- THOM, A. Blockage Corrections and Choking in the R.A.E. High Speed Tunnel ARC 2033 1943
- HACKETT, J.E. Tunnel-induced gradients and their effect on drag AIAA Journal 12 2575 2581 1996
- MASKELL, E. C. A theory of the blockage effects on bluff bodies and stalled wings in a closed wind tunnel ARC 3400 1965
- SCHLICHTING, H. Boundary layer theory 7th Edition McGraw-Hill Book 1979
- GARRY, K.P. WALLIS, S.B., COOPER, K.R., FEDIW, A. WILSDEN, D.J. The effect on aerodynamic drag of the longitudinal position of a road vehicle model in a wind tunnel test section SAE Technical Paper 940414 , Detroit 1994
- WICKERN, G. On the Application of Classical Wind Tunnel Corrections for Automotive Bodies SAE Technical Paper 2001-01-0633 , Detroit 2001
- MERCKER; E. COOPER, K.R., FISCHER, O. WIEDEMANN; J. The Influence of a Horizontal Pressure Distribution on Aerodynamic Drag in Open and Closed Wind Tunnels SAE Technical Paper 2005-01-0867 , Detroit 2005
- REICHARDT, H. ERMSHAUS, R.: Impuls- und Wärmeübertragung in turbulenten Windschatten hinter Rotationskörpern (Momentum and heat transfer in turbulent wakes behind axisymmetric bodies) Int. J. Heat Mass Transfer 5 251 265 1962
- STEINBACH, D. Calculation of Wall and Model Support Interferences in Subsonic Wind Tunnels ZfW 17 370 378 1993
- MOKRY, M. TEMPLIN, J.T.: A source panel method for the calculation of boundary interference on automobile models in solid and slotted walls and 3/4-open jet wind tunnels Canadian Aeronautics and Space Institute Aerodynamics Symposium Montreal 1985
- MOKRY, M. Assessment of Boundary Interference in Open Test Section Wind Tunnels Using Successive Over-Relaxation AIAA-2005-906 43rd AIAA Aerospace Sciences Meeting and Exhibit Reno, Nevada Jan. 10–13 2005
- WICKERN, G. SCHWARTEKOPP, B.: Correction of Nozzle Gradient Effects in Open Jet Wind Tunnels SAE Technical Paper 2004-01-0669 2004