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Trailing-edge flow manipulation using streamwise finlets

Published online by Cambridge University Press:  14 May 2019

Abbas Afshari Open the ORCID record for Abbas Afshari [Opens in a new window] ,
Mahdi Azarpeyvand ,
Ali A. Dehghan ,
Máté Szőke  and
Reza Maryami
Abbas Afshari
Affiliation:
Yazd University, Yazd, Iran
Mahdi Azarpeyvand*
Affiliation:
Department of Mechanical Engineering, University of Bristol, BristolBS8 1TR, UK
Ali A. Dehghan
Affiliation:
Yazd University, Yazd, Iran
Máté Szőke
Affiliation:
Department of Mechanical Engineering, University of Bristol, BristolBS8 1TR, UK
Reza Maryami
Affiliation:
Yazd University, Yazd, Iran
*
†Email address for correspondence: m.azarpeyvand@bristol.ac.uk
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Abstract

The use of streamwise finlets as a passive flow and aerodynamic noise-control technique is considered in this paper. A comprehensive experimental investigation is undertaken using a long flat plate, and results are presented for the boundary layer and surface pressure measurements for a variety of surface treatments. The pressure–velocity coherence results are also presented to gain a better understanding of the effects of the finlets on the boundary layer structures. The results show that the flow behaviour downstream of the finlets is strongly dependent on the finlet spacing. The use of finlets with coarse spacing leads to a reduction in pressure spectrum at mid- to high frequencies and an increase in spanwise length scale in the trailing-edge region due to flow channelling effects. For the finely distributed finlets, the flow is observed to behave similarly to that of a permeable backward-facing step, with significant suppression of the high-frequency pressure fluctuations but an elevation at low frequencies. Furthermore, the convection velocity is observed to reduce downstream of all finlet treatments. The trailing-edge surface pressure spectrum results have shown that, in order to obtain maximum unsteady pressure reduction, the finlet spacing should be of the order of the thickness of the inner layer of the boundary layer. A thorough study is provided for understanding of the underlying physics of both categories of finlets and their implications for controlling the flow and noise generation mechanism near the trailing edge.

JFM classification

Acoustics: Aeroacoustics Boundary Layers: Boundary layer control Turbulent Flows: Turbulent boundary layers
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 870 , 10 July 2019 , pp. 617 - 650
Copyright
© 2019 Cambridge University Press 

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Footnotes

A preliminary version of this paper was presented as Paper 2016-2834 at the 22nd AIAA/CEAS Aeroacoustics Conference, Lyon, France, 30 May–1 June 2016.

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