title: Extreme events in computational turbulence.
abstract: We have performed direct numerical simulations of homogeneous and isotropic turbulence in a periodic box with 8,192(3) grid points. These are the largest simulations performed, to date, aimed at improving our understanding of turbulence small-scale structure. We present some basic statistical results and focus on "extreme" events (whose magnitudes are several tens of thousands the mean value). The structure of these extreme events is quite different from that of moderately large events (of the order of 10 times the mean value). In particular, intense vorticity occurs primarily in the form of tubes for moderately large events whereas it is much more "chunky" for extreme events (though probably overlaid on the traditional vortex tubes). We track the temporal evolution of extreme events and find that they are generally short-lived. Extreme magnitudes of energy dissipation rate and enstrophy occur simultaneously in space and remain nearly colocated during their evolution.
authors.affiliation: Schools of Aerospace Engineering and Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332;
authors.forename: P K
authors.initials: PK
authors.lastname: Yeung
authors.affiliation: School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332;
authors.forename: X M
authors.initials: XM
authors.lastname: Zhai
authors.affiliation: Department of Physics, Department of Mechanical and Aerospace Engineering and Courant Institute of Mathematical Sciences, New York University, New York, NY 10012 krs3@nyu.edu.
authors.forename: Katepalli R
authors.initials: KR
authors.lastname: Sreenivasan
keywords: extreme events; fluid dynamics; intermittency; petascale computing; turbulence