Synchronization of large-scale coherent structures in vortex-gas free shear layers

Turbulent flows are chaotic systems characterized by sensitivity to initial conditions but can be ‘synchronized’ to a known solution by forcing the large scales in spectral space (Yoshida et al., Phys. Rev. Letters 94.1, 2005). Recently, this concept of synchronization in physical space for turbulent channel flow was studied by Wang & Zaki (J.Fluid Mech. 943, 2022) who showed that slabs of thickness of the local Taylor microscale can be synchronized. This talk aims to address the question whether the chaotic motion of the large-scale structures in turbulence can also be synchronized under certain circumstances. The vortex-gas shear layer is a chaotic Hamiltonian system relevant to the large-scale dynamics of a turbulent mixing layer. It has an interesting, underlying statistical mechanics (Suryanarayanan et al. Phys Rev. E 89.1, 2014), and provides a simpler setting to understand the concept of synchronization applied to free shear flows and large-scale coherent structures. Extensive numerical simulations are performed to understand the circumstances under which a shear layer can recreate the correct coherent structures when the evolution of neighboring structures is forcibly synchronized with a given solution. Implications for flow control are discussed.