Experimental measurements of
subgrid passive scalar anisotropy and universality

H. S. Kang(1) & C. Meneveau(1,2)
(1) Department of Mechanical Engineering,
(2) Center for Environmental & Applied Fluid MechanicsJohns Hopkins University, Baltimore, MD 21218, USA

ABSTRACT: An experimental study on the effects of passive scalar anisotropy on subgrid-scale (SGS) physics and modeling for Large Eddy Simulations is performed across a turbulent wake flow generated by a heated cylinder. To obtain filtered and subgrid quantities at three different filter sizes the separation distance among probes in an array of four X-wire and four cold-wire probes is varied. We find that while the kinetic energy dissipation tensor approaches isotropy at small scales, the SGS scalar-variance dissipation remains anisotropic independent of filter scale in the presence of the scalar gradient. The eddy-diffusion model predicts, incorrectly, isotropic behavior. The nonlinear (or tensor eddy diffusivity) model reproduces the correct trends, but overestimates the level of scalar dissipation anisotropy. The model coefficients evaluated from matching global averages of real and modeled SGS dissipations are fairly uniform across the wake (universal), both for those associated with the SGS momentum field and the anisotropic scalar field.

(2001) in Proceedings of Direct and Large Eddy Simulation -IV (Geurts, Métais and Friedrich, Eds).

full pdf article - (© Kluwer, see http://www.wkap.nl/kaphtml.htm/HOMEPAGE).