Publication: Three-dimensional Floquet stability analysis of the wake in cylinder arrays

All || By Area || By Year

Title Three-dimensional Floquet stability analysis of the wake in cylinder arrays
Authors/Editors* N. K.-R. Kevlahan
Where published* Journal of Fluid Mechanics
How published* Journal
Year* 2007
Volume 592
Pages 79-88
Publisher Cambridge University Press
Keywords tube arrays, Floquet stability analysis, fluid-structure interaction
Three-dimensional stability of the periodic wake of tightly packed rotated and inline cylinder arrays is investigated for 60<=Re<=270. Results are compared with existing numerical and experimental studies for an isolated cylinder. Numerical Floquet analysis shows that the two-dimensional wakes of the rotated and inline arrays with spacing P/D=1.5 become unstable at Re_c = 64+/-0.5 and Re_c = 132+/-1 respectively. Two-dimensional vortex shedding flow is unlikely in practice for such flows. The dominant spanwise wavelength is lambda/D=0.9+/-0.1 for the rotated array at Re=100 and lambda/D = 3.0 +/- 0.1 for the inline array at Re=200. Three-dimensional simulations show excellent agreement with the Floquet analysis for the rotated case, and reasonable agreement for the inline case. The instability mechanism appears to be similar to Mode A for an isolated cylinder, although the structure of the three-dimensional vorticity is different due to the spatial periodicity of the flow. Unlike the isolated cylinder, both array flows are unstable as lambda tends to infinity (like a thin shear layer). This is the first investigation of three-dimensional wake instability in cylinder arrays, a problem of significant practical and theoretical interest.
Go to Fluid Mechanics
Back to page 65 of list