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Flow past a transversely oscillating square cylinder in free stream at low Reynolds numbers
Author(s) -
Singh A. P.,
De A. K.,
Carpenter V. K.,
Eswaran V.,
Muralidhar K.
Publication year - 2008
Publication title -
international journal for numerical methods in fluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 112
eISSN - 1097-0363
pISSN - 0271-2091
DOI - 10.1002/fld.1979
Subject(s) - vortex shedding , wake , reynolds number , physics , mechanics , kármán vortex street , vortex , natural frequency , amplitude , cylinder , geometry , vibration , turbulence , mathematics , optics , acoustics
This paper reports simulation results for free‐stream flow past an oscillating square cylinder at Re =100 and 150, for oscillating‐to‐natural‐shedding frequency ratios of 0.5⩽ f r ⩽3.0 at a fixed oscillation amplitude of 0.2 of the cylinder width. The transformed governing equations are solved in a non‐inertial frame of reference using the finite volume technique. The ‘lock‐in’ phenomena, where the vortex shedding becomes one with the oscillation frequency, is observed near the natural shedding frequency ( f r ≈1). Beyond the synchronization band, downstream recovery of the wake to its stationary (natural) state (frequency) is observed in cross‐stream velocity spectra. At higher forcing frequencies, a phase lag between the immediate and the far wake results in a shear layer having multi‐polar vortices. A ‘Vortex‐switch’ accompanied by a change in the direction of energy transfer is identified at the ‘lock‐in’ boundaries. The variation of aerodynamic forces is noticed to be different in the lock‐in regime. The velocity phase portrait in the far wake revealed a chaotic state of flow at higher excitation though a single (natural) frequency appears in the spectra. Copyright © 2008 John Wiley & Sons, Ltd.