High-frequency forcing of a turbulent axisymmetric wake
File(s)
Accepted version
Author(s)
Oxlade, AR
Morrison, JF
Qubain, A
Rigas, G
Type
Journal Article
Abstract
A high-frequency periodic jet, issuing immediately below the point of separation, is used to force the turbulent wake of a bluff axisymmetric body, its axis aligned with the free stream. It is shown that the base pressure may be varied more or less at will: at forcing frequencies several times that of the shear layer frequency, the time-averaged area-weighted base pressure increases by as much as 35 %. An investigation of the effects of forcing is made using random and phase-locked two-component particle image velocimetry (PIV), and modal decomposition of pressure fluctuations on the base of the model. The forcing does not target specific local or global wake instabilities: rather, the high-frequency jet creates a row of closely spaced vortex rings, immediately adjacent to which are regions of large shear on each side. These shear layers are associated with large dissipation and inhibit the entrainment of fluid. The resulting pressure recovery is proportional to the strength of the vortices and is accompanied by a broadband suppression of base pressure fluctuations associated with all modes. The optimum forcing frequency, at which amplification of the shear layer mode approaches unity gain, is roughly five times the shear layer frequency.
Date Issued
2015-05-10
Date Acceptance
2015-03-05
Citation
Journal of Fluid Mechanics, 2015, 770 (1), pp.305-318
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
305
End Page
318
Journal / Book Title
Journal of Fluid Mechanics
Volume
770
Issue
1
Copyright Statement
© Cambridge University Press 2015. High-frequency forcing of a turbulent axisymmetric wake. Anthony R. Oxlade, Jonathan F. Morrison, Ala Qubain and Georgios Rigas. J. Fluid Mech. (2015), vol. 770, pp. 305–318. The final publication is available via Cambridge Journals Online at https://dx.doi.org/10.1017/jfm.2015.153
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/highfrequency-forcing-of-a-turbulent-axisymmetric-wake/FCE8FA105B14246D5B01ABC9D2F64045
Grant Number
EP/I005684/1
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
instability control
turbulence control
wakes
BLUFF-BODY
POISSONS-EQUATION
REYNOLDS-NUMBERS
FEEDBACK-CONTROL
FLOW
PRESSURE
SUPPRESSION
BODIES
SPHERE
LAYER
Publication Status
Published
Date Publish Online
2015-03-31