The stochastic-parametric mechanism in turbulent boundary layers: how nonlinearity and non-normality interact to self-sustain the turbulent state
Abstract
A fundamental problem in turbulence is understanding the mechanism by which energy is systematically transferred from the externally driven mean flow to the turbulent perturbation field. The optimally growing non-normal structure in boundary layers, the roll/streak, dominates this transfer, but it is linearly stable. In order to maintain the turbulent perturbation field the roll/streak structure must be destabilized nonlinearly by second order interaction with the perturbation field. However, there are no stable stationary solutions for this interaction instability, so the statistically steady turbulent state is necessarily time-dependent. In this presentation the mechanism by which the perturbation field and the roll/streak together sustain the turbulent state through their mutual interaction is analyzed. This mechanism is parametric, nonlinear, non-normal, and essentially time-dependent. Simulations demonstrating this parametric mechanism will be shown, including an example in which the stochastic-parametric mechanism sustains turbulence in a flow that is Rayleigh-stable at each instant.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMNG43B1489F
- Keywords:
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- 4490 NONLINEAR GEOPHYSICS / Turbulence