mixing layer

isotropic turbulence

turbulent flows

Physical Review Letters

An intrinsic feature of turbulent flows is an enhanced rate of mixing and\nkinetic energy dissipation due to the rapid generation of small-scale motions\nfrom large-scale excitation. The transfer of kinetic energy from large to small\nscales is commonly attributed to the stretching of vorticity by the\nstrain-rate, but strain self-amplification also plays a role. Previous\ntreatments of this connection are phenomenological or inexact, or cannot\ndistinguish the contribution of vorticity stretching from that of strain\nself-amplification. In this paper, an exact relationship is derived which\nquantitatively establishes how intuitive multi-scale mechanisms such as\nvorticity stretching and strain self-amplification together actuate the\ninter-scale transfer of energy in turbulence. Numerical evidence validates this\nresult and uses it to demonstrate that the contribution of strain\nself-amplification to energy transfer is higher than that of vorticity\nstretching, but not overwhelmingly so.\n

Energy Transfer from Large to Small Scales in Turbulence by Multiscale Nonlinear Strain and Vorticity Interactions