Chinese Journal of Aeronautics
Jump to content
Volume Author Title Keywords DOI Advanced
Impact factor:1.307
SCI ranking:Q2 Publisher:Elsevier
Call for Paper
Aims and Scope
Editorial Board
Online Submission
Author Information
Online Review
Reviewer Information
      Journal Services
Email Alert
Read the Article
No.4, Vol.30, 2017
2017 Vol. 30 (4): 0-0 [Abstract] ( 7 ) HTML (1 KB)  PDF (26933 KB)   ( 49 )
Wake structure and similar behavior of wake profiles downstream of a plunging airfoil

Very limited attention has already been paid to the velocity behavior in the wake region in unsteady aerodynamic problems. A series of tests has been performed on a flapping airfoil in a subsonic wind tunnel to study the wake structure for different sets of mean angle of attack, plunging amplitude and reduced frequency. In this study, the velocity profiles in the wake for various oscillation parameters have been measured using a wide shoulder rake, especially designed for the present experiments. The airfoil under consideration was a critical section of a 660 kW wind turbine. The results show that for a flapping airfoil the wake structure can be of drag producing type, thrust producing or neutral, depending on the mean angle of attack, oscillation amplitude and reduced frequency. In a thrust producing wake, a high-momentum high-velocity jet flow is formed in the core region of the wake instead of the conventional low-momentum flow. As a result, the drag force normally experienced by the body due to the momentum deficit would be replaced by a thrust force. According to the results, the momentum loss in the wake decreases as the reduced frequency increases. The thrust producing wake pattern for the flapping airfoil has been observed for sufficiently low angles of attack in the absence of the viscous effects. This phenomenon has also been observed for either high oscillation amplitudes or high reduced frequencies. According to the results, for different reduced frequencies and plunging amplitudes, such that the product of them be a constant, the velocity profiles exhibit similar behavior and coalesce on each other. This similarity parameter works excellently at small angles of attack. However, at near stall boundaries, the similarity is not as evident as before.

2017 Vol. 30 (4): 1281-1293 [Abstract] ( 36 ) HTML (1 KB)  PDF (3883 KB)   ( 32 )
Chinese Journal of Aeronautics
About CJA
Contact CJA
Online Submission
© 2011 Chinese Journal of Aeronautics. All Rights Reserved.