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A comparison of the wake structure of a stationary and oscillating bluff body, using a conditional averaging technique

Published online by Cambridge University Press:  29 March 2006

M. E. Davies
M. E. Davies
Affiliation:
Department of Aeronautics, Imperial College, London Present address: Division of Maritime Science, National Physical Laboratory, Teddington, Middlesex, England.
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Abstract

A conditional averaging technique to extract the underlying vortex pattern from a turbulent bluff body wake is described. Ensemble averages of wake velocities are developed on the basis of a reference phase position, determined from the outer flow irrotational fluctuations. The method is applied to the wakes of a stationary and oscillating D-shape cylinder, where, in the latter case, the vortex shedding is locked to the frequency of body movement. Direct comparisons of average circulation and vortex street spacings are obtained and these demonstrate the significant change in wake structure that accompanies and sustains vortex-induced vibrations. It is observed in both conditions that only 25% of the estimated shed vorticity is found in the fully developed wake. In addition the analysis produces profiles of vorticity and velocity in an ‘average vortex cycle’. A model, developed to help interpret these results, suggests that a good representation of an average wake situation is obtained by the addition of considerable mean shear to a street of finite area axisymmetric vortices.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 75 , Issue 2 , 27 May 1976 , pp. 209 - 231
Copyright
© 1976 Cambridge University Press

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References

Berger, E. 1964 Die Bestimmung der hydrodynamischen Grössen einen Karmanschen Wirbelstrasse aus Hitzdrahtmessungen bei kleinen Reynoldschen Zahlen Z. Flugwiss. 12, 41.Google Scholar
Bloor, M. S. & Gerrard, J. H. 1966 Measurements of turbulent vortices in a cylinder wake. Proc. Roy. Soc. A 294, 319.Google Scholar
Clements, R. R. 1973 An inviscid model of two-dimensional vortex shedding J. Fluid Mech. 57, 321.Google Scholar
Davies, M. E. 1975 Wakes of oscillating bluff bodies. Ph.D. thesis, University of London.
Dwyer, H. A. & Mccroskey, W. J. 1973 Oscillating flow over a cylinder at large Reynolds number J. Fluid Mech. 61, 753.Google Scholar
Face, A. & Johansen, F. C. 1927 The flow of air behind an inclined flat plate of infinite span. Aero. Res. Counc. R. & M. no. 1104.Google Scholar
Feng, C. C. 1968 The measurement of vortex induced effects in now past stationary and oscillating circular and D-section cylinders. M.A.Sc. thesis, Department of Mechanical Engineering, University of British Columbia.
Ferguson, N. & Parkinson, G. 1967 Surface and wake phenomena of vortex-excited oscillations of bluff cylinders Trans. A.S.M.E., J. Engng Indust. 89, 831.Google Scholar
Gerrard, J. H. 1966 The mechanics of the formation region of vortices behind bluff bodies J. Fluid Mech. 25, 401.Google Scholar
Griffin, O. M. 1972a The effects of synchronized cylinder vibrations on vortex formation and strength, velocity fluctuations and mean flow. IUTAM Symp. Flow Induced Structural Vibrations, Karlsruhe, session E.
Griffin, O. M. 1972a Flow near self-excited and forced vibrating circular cylinders. Trans. A.S.M.E., J. Engng Indust. 94, 539.Google Scholar
Hartlen, R. & Currie, I. 1970 A lift-oscillator model for vortex-induced vibrations Proc. A.S.C.E., J. Engng Mech. 96, 577.Google Scholar
Hoffman, E. R. & Joubert, P. N. 1963 Turbulent line vortices J. Fluid Mech. 16, 395.Google Scholar
Kaden, H. 1931 Aufwicklung einer unstabilen Unstetigkeitsfläche Ing. Arch. 2, 140. (See also R.A.E. Lib. Trans. no. 403, 1952.)Google Scholar
Koopmann, G. H. 1967 The vortex wakes of vibrating cylinders at low Reynolds numbers J. Fluid Mech. 28, 501.Google Scholar
Novak, M. & Tanaka, H. 1975 Pressure correlations on a vibrating cylinder. Proc. 4th Int. Conf. Wind Effects on Buildings & Structures, Heathrow, London.Google Scholar
Roshko, A. 1954 On the drag and shedding frequency of two-dimensional bluff bodies. N.A.C.A. Tech. Note, no. 3169.Google Scholar
Saffman, P. G. 1973 Structure of turbulent line vortices Phys. Fluids, 16, 1181.Google Scholar
Sarpkaya, T. 1975 An inviscid model of two-dimensional vortex shedding for transient and asymptotically steady separated flow over an inclined plate J. Fluid Mech. 68, 109.Google Scholar
Schaeffer, J. & Eskinazi, S. 1959 An analysis of the vortex street generated in a viscous fluid J. Fluid Mech. 6, 241.Google Scholar
Timme, A. 1957 Über die Geschwindigkeitsverteilung in Wirbeln Ing. Arch. 25, 205.Google Scholar
Toebes, G. H. 1967 Symp. Wind Effects on Buildings & Structures, vol. 2, paper 37. Nat. Res. Counc. Can.