Abstract
The hydrodynamics and flow structures of a base wing slotted with tip sails in proximity to the ground were studied experimentally in order to investigate the flow control efficiency of wing tip sails in ground effect. The experiment was conducted in a towing tank at a Reynolds number 1.5×105. The lift and drag forces were measured by a transducer, the velocity fields of the wing tip vortices were measured using a time-resolved particle image velocimetry system (TR-PIV). The tip-sails and ground clearance were both effective in reducing the total drag, the lift coefficients of the tip-sails wings were increased as compared with that of a base wing. The lift-drag ratios of the tip-sails wings were improved obviously in a range of angles of attack from 2° to stalling angle. The tip-sails played more important role in unwinding the concentrated wing tip vortices at higher angle of attack, the intensity of the tip vortices were much weaker than that of the base wing. The development of the wing tip vortices was suppressed as well due to the inhibition of the ground, the downwash speed was reduced and the induced drag was decreased.
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Acknowledgements
The authors would like to thank Mr. Dai-feng Wang and Jun Xia for all their help with the experimental facilities. We express appreciation to Mr. Cheng Cheng for the data processing and figure plotting. We thank the anonymous referees for the insightful comments and suggestions on this manuscript.
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Project supported by the National Natural Science Foundation of China (Grant No. 11472169).
Biography: Jian-xun Zhou (1993-), Male, Ph. D. Candidate
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Zhou, Jx., Sun, Ch. & Daichin Drag reduction and flow structures of wing tip sails in ground effect. J Hydrodyn 32, 93–106 (2020). https://doi.org/10.1007/s42241-020-0006-4
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DOI: https://doi.org/10.1007/s42241-020-0006-4