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Energy Transfer Mechanisms in Wall-Bounded Turbulent Flows using Generalized Quasilinear Approximations

AMS Seminar Series

Speaker: Carlos Gonzalez Hernandez, Stanford University

Presentation

Seminar Slide Deck (PDF-3.3MB)

Abstract

Finding a reliable and accurate low-dimensional statistical description for a turbulent flow has been a long-standing challenge for many decades. Despite the highly chaotic and multiscale nature, one of the increasingly evident features is that at least some features of energy-containing motions (i.e., coherent structures) in turbulent shear flows appear to be qualitatively well described by the Navier–Stokes equations linearized around the mean velocity. Despite the progress made up to now, the linearly stable nature of the mean velocity in the canonical wall-bounded turbulent flows implies that solely the linearized Navier–Stokes equations are not able to describe sustaining velocity fluctuations. From this perspective, the recent quasilinear-type (QL) modelling is an appealing direction to pursue. Common to all variations of this approach is a decomposition of the given flow into two groups: one in which all nonlinear terms are kept, and the other in which all self-interactions are ignored or suitably modeled. In this talk, I will analyse the spectral energetics of the QL model applied to a homogeneous shear turbulent flow and channel flow, in particular its effect on the energy cascade and the damage of the pressure-strain transport. This model will be generalized (Marston et al. 2016, PRL) and it will be shown that the further incorporation of a small number of Fourier modes into the first group reasonably well recovers the distance-from-the-wall scaling in the turbulence statistics and spectra. Finally, I will show how the generalized quasilinear approximation can be used as an interventional tool to study scale interactions in wall-bounded flows.

Biography

Photo of Carlos Gonzalez Hernandez
Carlos Gonzalez Hernandez is a Research Fellow in the Department of Aeronautics & Astronautics at Stanford University. He works at the intersection of Computational Fluid Dynamics and Artificial Intelligence, specializing in the construction of digital twins via physics-informed reduced-order models (ROMs) for turbulent flows across scales, with a focus on Hypersonics. He has made breakthrough contributions in the field of laminar to turbulent transition at high speeds and his work pioneered the use of interventional tools to suppress triadic nonlinear interactions in wall-bounded turbulent flows. He received a B.S. and M.S. in Aerospace Engineering from University of Seville, and a M.S. in Fluid Mechanics from Ecole Polytechnique. He holds a Ph.D. from Imperial College London on receptivity of transitional boundary layers in supersonic regime. His current interests include high-speed boundary layers, wall-bounded turbulence and reduced-order models.