Scalar Mixing In A Vortex Flow
Abstract
We present experimental and theoretical results on the evolution of a scalar blob em- bedded in the velocity field of one or two vortices, a configuration relevant to geo- physical mixing in particular.
We first follow the evolution of the scalar in one vortex. The scalar blob rolls up into a spiral and then diffuses rapidly, much faster than in the absence of a vortex flow. A simple model predicts that the maximal scalar concentration decreases in time as t-3 , after a mixing time which scales like Pe1 /2 /3 (where Pe = /D is the Peclet number). This hyper-diffusion process is due to the coupled presence of stretching and diffusion, and is in good quantitative agreement with the experimental results. In contrast with this temporal variation of the scalar, the model predicts that the proba- bility distribution functions (PDF) of the scalar are almost stationnary. The agreement between experimental and theoretical PDF is excellent. Finally, we report on the evolution of the PDF of a scalar during the merging of two vortices and on the comparison law of the concentration PDF's associated with each vortices, both in laminar and turbulent situations.- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.4429M