GALCIT Home Page
| 2000-2001 Fluids Seminar Page |
Mechanical and Aerospace Engineering
Cornell University
Abstract-
Understanding intermittency, the strong variability in dissipation and mixing
rates in fully developed turbulence, remains an outstanding and central
problem. Here I describe high Reynolds number experiments (up to a Taylor
scale Reynolds number of 1000) done in wind-tunnel homogeneous shear flow.
Our results show that the higher order odd moments of the velocity
derivatives and differences measured along the shear do not tend to zero at
high Reynolds number, indicating a violation of the postulate of local
isotropy. The results, both for the dissipation and inertial range, suggest
that extreme anisotropic events from the large scales penetrate to the small
scales, by-passing the cascade. This direct coupling between the large and
small scales results in the small scale anisotropy as well as in the
intermittency: it will be shown that they are interconnected phenomena.
Similar findings for passive scalars (temperature, humidity, species
concentration) will be discussed and related to problems of mixing both in
the laboratory and atmosphere.
|
GALCIT Home Page
|
|