# Fluid Mechanics and Acoustics Laboratory - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique
Lyon
France

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Article in Phys. Rev. E (2020)

## Linearly forced isotropic turbulence at low Reynolds numbers

Wouter Bos, Faouzi Laadhari & Wesley Agoua

The forcing strength needed to sustain a flow using linear forcing is investigated. A critical Reynolds number $R_c$ is determined, based on the longest wavelength allowed by the system, the forcing strength and the viscosity. A simple model is proposed for the dissipation rate, leading to a closed expression for the kinetic energy of the flow as a function of the Reynolds number. The dissipation model and the prediction for the kinetic energy are assessed using direct numerical simulations and two-point closure integrations. An analysis of the dissipation-rate equation and the triadic structure of the nonlinear transfer allows to refine the model in order to reproduce the low-Reynolds-number asymptotic behavior, where the kinetic energy is proportional to $R−R_c$.