Title of article :
Coherent vortical and straining structures in the finite wall-mounted square cylinder wake
Author/Authors :
Bourgeois، نويسنده , , J.A. and Sattari، نويسنده , , P. and Martinuzzi، نويسنده , , R.J.، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2012
Pages :
11
From page :
130
To page :
140
Abstract :
Topological aspects of the turbulent wake of a finite, surface-mounted, square-cross-section cylinder of h/d = 4 are addressed by decomposing the velocity field into a quasi-periodic coherent part and the unresolved incoherent fluctuations. The three-dimensional large scale structure is educed through a reconstruction of planar phase-averaged PIV measurements using the simultaneously sampled surface pressure difference on opposing sides of the obstacle as a phase reference. A topological model for the vortex structure is educed and mean streamwise wake vorticity is explained in terms of the connections between initially vertical structures shed alternately from either side of the obstacle, rather than previously proposed ‘tip’ vortex structures generated at the obstacle free-end. The coherent structure educed accounts for a significant portion of the fluctuating energy in the wake. The turbulent field is further analyzed by finding Lagrangian straining structures that form by induction of the coherent vorticity field, and these structures are related to the energy transfer from the base phase-averaged flow since they act to stretch incoherent vorticity fluctuations in their neighbourhood.
Keywords :
Finite time Lyapunov exponent , Turbulence production , Vortex shedding , Coherent structures
Journal title :
International Journal of Heat and Fluid Flow
Serial Year :
2012
Journal title :
International Journal of Heat and Fluid Flow
Record number :
2382074
Link To Document :
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