ACTA AERONAUTICAET ASTRONAUTICA SINICA >
Test on controlling coherent structure of separated shear flow by bionic coverts
Received date: 2024-02-03
Revised date: 2024-03-11
Accepted date: 2024-04-03
Online published: 2024-04-19
Supported by
National Natural Science Foundation of China(12372278);the Foundation of National Key Laboratory of Science and Technology on Aerodynamic Design and Research(61422010301);the Open Project Program of the Key Laboratory of Aerodynamic Noise Control(ANCL20230108);the Foundation of State Key Laboratory of Rail Transit Vehicle System(TPL2306);the Sino-German Center for Research Promotion-Mobility Program(GZ1575)
The flexible serrated coverts on the upper wing of the owl play an effective role in controlling flow separation and reducing acoustic noise. In this paper， wind tunnel experiments were conducted to study the flow control effectiveness of the flexible serrated coverts structures on the large-scale coherent structures in the parallel shear flow downstream of backward-facing step. In the experiment， the bionic coverts of different thicknesses were installed on the step edge， and were driven to adaptively flutter by the air flow. The turbulent velocity in the downstream were measured by the hot wire anemometer， and the coherent features were analyzed in both the time and frequency domains. The results show that the coverts of different thicknesses were capable of controlling flow separation， reducing turbulent fluctuation intensity， and suppressing the generation of the large-scale coherent structures within the shear layer. Among them， the coverts of 0.2 mm show the most effective results， which reduced the separation length by approximately 20% and decreased the turbulent intensity peaks by approximately 30%. Furthermore， wavelet analysis shows that adaptive fluttering motions had the effect of “fluttering-combing” the separated shear layer downstream of backward-facing step， suppressing the spanwise generation of high- and low-speed streaks， and reducing the proportion of low-frequency large-scale coherent structures. The experimental study shows the flow control effect of flexible serrated coverts of birds， and reveals the underlying mechanism of flow separation control and acoustic noise reduction.
Key words： bionics; covert; flow control; separated shear layer; coherent structure
Yihong LIU , Xingyu MA , Jiateng PAN , Nan JIANG . Test on controlling coherent structure of separated shear flow by bionic coverts[J]. ACTA AERONAUTICAET ASTRONAUTICA SINICA, 2024 , 45(23) : 630284 -630284 . DOI: 10.7527/S1000-6893.2024.30284
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