#### DIMOTAKIS, P. E., CATRAKIS, H. J., COOK, A. W., AND PATTON, J. M. 1998
"On the geometry of two-dimensional slices of irregular level sets in turbulent flows,"
*2*^{nd} Monte-Verita Colloquium on Fundamental Problematic Issues in Turbulence (22-28 March 1998, Ascona, Switzerland).
GALCIT Report FM98-2.

*Abstract*

Isoscalar surfaces in turbulent flows are found to be more complex than
(self-similar) fractals, in both the far field of liquid-phase turbulent jets
and in a realization of Rayleigh-Taylor-instability flow.
In particular, they exhibit a scale-dependent coverage dimension,
D_{2}(l),
for 2-D slices of scalar level sets,
that increases with scale, from unity, at small scales, to 2, at large scales.
For the jet flow and Reynolds numbers (Re) investigated, the isoscalar-surface geometry is both scalar-threshold- and Re-dependent;
the level-set (coverage) length decreases with increasing Re, indicating
enhanced mixing with increasing Reynolds number; and the size distribution of
closed regions is well described by lognormal statistics at small scales.
A similar D_{2}(l) behavior is found for level-set data of 3-D density-interface behavior in recent direct numerical-simulation studies of Rayleigh-Taylor-instability flow.
A comparison of (spatial) spectral and isoscalar coverage statistics are discussed.

GALCIT Report FM98-2 (PDF file, 593KB). Downsampled to 150dpi to reduce file size.
Copyright © 1998 Paul E. Dimotakis.