POF Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Sep 2010

Volume 22, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Phys. Fluids 22, 091106 (2010); http://dx.doi.org/10.1063/1.3483215 (1 page)

D. M. Harris, V. A. Miller, and C. H. K. Williamson
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds
back to top Laminar Flows

Vortex decay in the Kármán eddy street

Fernando L. Ponta

Phys. Fluids 22, 093601 (2010); http://dx.doi.org/10.1063/1.3481383 (11 pages) | Cited 1 time

Online Publication Date: 15 September 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, we analyze the effect of viscosity on the vorticity distribution and its rate of decay in the Kármán vortex street behind a circular cylinder. We used direct numerical simulation data, which we compare to well-known experimental measurements. By decomposing the incompressible velocity field in a frame of reference attached to the cylinder into its solenoidal and harmonic components, we identify the eddy structures associated with the formation, shedding, and rearrangement of the vortices into the Kármán street, and study their subsequent decay. This allows us to extend the conclusions of the partially viscous model by Hooker [“On the action of viscosity in increasing the spacing ratio of a vortex street,” Proc. R. Soc. London, Ser. A 154, 67 (1936)] , who made several simplifying hypotheses: initial infinite-length filament-vortex wake, circular Lamb vortices of equal age at subsequent times, and no overlapping of the vortex cores. We show that the vortices have elliptical cores with an elliptical ratio that evolves downstream according to a systematic law. We also find that the vortex cores exhibit a Gaussian vorticity profile and a vorticity versus stream-function scatter plot clearly consistent with the Lamb-vortex model. The peak vorticity in the core decays downstream with a hyperbolic decay rate determined by the amount of circulation contained in the core at the early stages of the street, which is also consistent with Lamb’s solution.
Show PACS
47.11.-j Computational methods in fluid dynamics
47.27.E- Turbulence simulation and modeling
47.32.-y Vortex dynamics; rotating fluids

Oscillatory instability of a three-dimensional lid-driven flow in a cube

Yuri Feldman and Alexander Yu. Gelfgat

Phys. Fluids 22, 093602 (2010); http://dx.doi.org/10.1063/1.3487476 (9 pages) | Cited 4 times

Online Publication Date: 30 September 2010

Full Text: Read Online (HTML) | Download PDF

multimedia

Show Abstract
A series of time-dependent three-dimensional (3D) computations of a lid-driven flow in a cube with no-slip boundaries is performed to find the critical Reynolds number corresponding to the steady-oscillatory transition. The computations are done in a fully coupled pressure-velocity formulation on 1043, 1523, and 2003 stretched grids. Grid-independence of the results is established. It is found that the oscillatory instability of the flow sets in via a subcritical symmetry-breaking Hopf bifurcation at Recr ≈ 1914 with the nondimensional frequency ω = 0.575. Three-dimensional patterns in the steady and oscillatory flow regimes are compared with the previously studied two-dimensional configuration and a three-dimensional model with periodic boundary conditions imposed in the spanwise direction.
Show PACS
47.20.Ky Nonlinearity, bifurcation, and symmetry breaking
47.54.-r Pattern selection; pattern formation
47.15.Rq Laminar flows in cavities, channels, ducts, and conduits
47.10.A- Mathematical formulations
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close