The squeezes, stretches, and whirls of turbulence

Perry Johnson, UC Irvine

Friday, October 29, 2021
1:30 p.m.

The phenomenon of turbulence in fluid flows is a paradigmatic nonlinear multiscale dynamical system in classical physics with important implications for a wide range of natural and engineered flows. A central pillar of turbulence theory is the kinetic energy cascade, which accounts for the rapid production of small-scale activity from large-scale excitation via interscale energy transfer. For the better part of a century, the energy cascade has been phenomenologically attributed to a mechanism known as vortex stretching. More recently, some have expressed dissatisfaction with this view and have identified an alternative mechanism: strain self-amplification. In this talk, I will demonstrate that interscale energy transfer may be expressed exactly in terms of vorticity stretching and strain self-amplification, including the role of multiscale interactions. The result provides a holistic view of turbulent energetics in both two- and three-dimensional flows. Implications and future directions for modeling and simulation will be discussed.