Comparison of data correction methods for blockage effects in semispan wing model testing

Anwar U Haque,Erwin Sulaeman,Waqar Asrar,Ashraf A Omar,Mohamed J.S Ali,P Dančová,M Veselý

doi:10.1051/epjconf/201611402129

Anwar U Haque, Erwin Sulaeman + Show 5 more

Open Access

https://doi.org/10.1051/epjconf/201611402129

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Abstract

Wing alone models are usually tested in wind tunnels for aerospace applications like aircraft and hybrid buoyant aircraft. Raw data obtained from such testing is subject to different corrections such as wall interference, blockage, offset in angle of attack, dynamic pressure and free stream velocity etc. Since the flow is constrained by wind tunnel walls, therefore special emphasis is required to deliberate the limitation of correction methods for blockage correction. In the present research work, different aspects of existing correction methods are explored with the help of an example of a straight semi-span wing. Based on the results of analytical relationships of standard methods, it was found that although multiple variables are involved in the standard methods for the estimation of blockage, they are based on linearized flow theory such as source sink method and potential flow assumption etc, which have intrinsic limitations. Based on the computed and estimated experimental results, it is recommended to obtain the corrections by adding the difference in results of solid walls and far-field condition in the wind tunnel data. Computational Fluid Dynamics technique is found to be useful to determine the correction factors for a wing installed at zero spacer height/gap, with and without the tunnel wall.

Highlights

One of the major problems associated with the wind tunnel test for a wing is the blockage effects produced by the wind tunnel walls [1]
Since the flow is constrained by wind tunnel walls, special emphasis is required to deliberate the limitation of correction methods for blockage correction
Based on the results of analytical relationships of standard methods, it was found that multiple variables are involved in the standard methods for the estimation of blockage, they are based on linearized flow theory such as source sink method and potential flow assumption etc, which have intrinsic limitations

Summary

Introduction

One of the major problems associated with the wind tunnel test for a wing is the blockage effects produced by the wind tunnel walls [1]. Wind tunnel testing on a wing or lifting body will have too little downwash, as the wing appears to have a larger effective aspect ratio than it would have if tested in free air These effects are small if the span is much less than the tunnel width, but large span models produce serious distortions in lift distribution which affect stalling characteristics [4]. To alleviate such interference, a correction scheme to cater the blockage effects is always required. Deficiencies in such correction procedure are likely to be most severe when the model is mounted on the tunnel’s floor and the interference flow created by such an arrangement has significant non-uniformity in the region of the model [5]

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Conclusion