https://stockholmuniversity.zoom.us/j/940229961
Employing the response function formalism in turbulence closure is a way to construct a self-consistent theory without resorting to any parameters. The multiple-scale direct-interaction approximation (DIA) analysis enables us to treat the non-equilibrium effect of turbulence through the Lagrangian derivative of the turbulence fields. In some turbulent flows such as homogeneous-shear turbulence, the injection rate of energy increases with time, and the energy dissipation process cannot catch up with the energy injection at the energy-containing scale. Such effect cannot be properly described by simple eddy-viscosity concept based on the equilibrium property of the turbulence inertial range. In this talk, two cases, where the non-equilibrium effect plays an essential role, will be presented. First, the turbulent energy flux associated with plumes are analysed and modelled in the double filtering procedure in the time and space domains. Second, the role of cross-interaction response functions is presented in the context of dynamos. In the presence of non-equilibrium properties of magnetohydrodynamic turbulence, additional dynamo effects are expected to appear through the cross-interaction responses.
References
Yokoi, N., Masada, Y., and Takiwaki, T. “Modelling stellar convective transport with plumes - I. Non-equilibrium turbulence effect in double-averaging formulation,” MNRAS, 516, 2718–2735 (2022).
https://doi.org/10.1093/mnras/stac1181
Yokoi, N. “Unappreciated cross-helicity effects in plasma physics: Anti-diffusion effects in dynamo and momentum transport,” (2023). http://arxiv.org/abs/2303.01834
Mizerski, K., Yokoi, N., and Brandenburg, A. “Cross-helicity effect on α-type dynamo in non-equilibrium turbulence” (2023).
http://arxiv.org/abs/2303.01834