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James G. Brasseu, Pennsylvania State University, APS Faculty Fellow, NCAR
The Kolmogorov 1941 (K41) phenomenology dominates our understanding of internal interscale dynamics within high Reynolds number free turbulence. In particular, K41 underlies a description of inertial turbulence dynamics that is restricted, on average, to nonlinear interactions among turbulence motions that are commensurate in scale. Thus, the small-scale dissipation-dominant turbulence motions dynamically communicate with the large-scale energy-dominant motions only indirectly, through a sea of local scale interactions that progressively isotropize turbulence structure as energy and momentum move to progressively smaller scales. Kolmogorov dynamics, however, is restricted to turbulence in equilibrium. There exist potentially useful unexplored nonlinear interscale dynamics when turbulence is forced out of equilibrium. I will address three interrelated dynamics in a general discussion of scale interactions in high Reynolds number free turbulence, contrasting equilibrium and nonequilibrium turbulence dynamics: (1) fundamental issues of energy exchange within triadic interactions and general features of “local,” “non-local,” and “distant” triadic interactions, (2) nonclassical interscale inertial dynamics as fully developed isotropic decaying turbulence is anisotropically forced from equilibrium, and (3) a study in which the phase changes at the small scales are found to be strongly influenced by distant triadic interactions in stationary isotropically forced turbulence.
Tuesday, March 6, 2012RefreshmentsMesa Laboratory, Main AuditoriumLecture at 11:00am