Alternative ways of looking at scale interactions in wall turbulence
Time: Thu 2018-10-18 10.30
Lecturer: Davide Gatti
Location: Faxen, FPL, Teknikringen 8
Abstract The hallmark feature of turbulent wall-bounded flows is the multiscale, anisotropic and inhomogenous nature. Despite the availability of high-fidelity three-dimensional flow data, a comprehensive description of the structure of inhomogeneous turbulent flows is still challenging. One factor limiting our understanding is the difficulty to simultaneously grasp both scale and spatial properties of turbulence. In this talk, I will introduce a theoretical framework for assessing the scale properties of anisotropic and inhomogenous turbulent flows, based on the exact budget equations for each component of the second order structure function tensor. These equations, also named Anisotropic Generalized Kolmogorov Equations (AGKEs), are an interesting alternative to studying turbulent spectra, provide a natural definition of scales also in the inhomogeneous directions and give prominence to the transfer of Reynolds stresses across scales and in space. I will demonstrate the use of the AGKEs, together with other classic instruments, on turbulent channels. In particular, a toy problem will be used to describe the interactions between Very Large Scale Motions and other scales of turbulence.