a1 Schools of Aerospace Engineering, Computational Science and Engineering, and Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
a2 Department of Aerospace Engineering, Texas A&M University, College Station, TX 77843, USA
a3 Courant Institute of Mathematical Sciences and Physics Department, New York University, New York, NY 10012, USA
We use data from well-resolved direct numerical simulations at Taylor-scale Reynolds numbers from 140 to 1000 to study the statistics of energy dissipation rate and enstrophy density (i.e. the square of local vorticity). Despite substantial variability in each of these variables, their extreme events not only scale in a similar manner but also progressively tend to occur spatially together as the Reynolds number increases. Though they possess non-Gaussian tails of enormous amplitudes, ratios of some characteristic properties can be closely linked to those of isotropic Gaussian random fields. We present results also on statistics of the pressure Laplacian and conditional mean pressure given both dissipation and enstrophy. At low Reynolds number intense negative pressure fluctuations are preferentially associated with rotation-dominated regions but at high Reynolds number both high dissipation and high enstrophy have similar effects.
(Received October 31 2011)
(Reviewed December 30 2011)
(Accepted December 31 2011)
(Online publication February 08 2012)