Coherent structures from the linearized Navier–Stokes equations for turbulent wall-bounded flows

Abstract: Turbulent fluid flows are ubiquitous in many natural and engineering systems. The modelling of these flows is a challenging, but crucial aspect of understanding a variety of problems with significant social and economic impact. It is therefore remarkable that predicting these turbulent flows in many instances comes down to modelling the ‘coherent structures’ of these flows. These coherent structures are organised patterns (or flow features) that appear in turbulent flows and play significant roles in the dynamics of the flow. The focus of this talk is the modelling of these coherent structures in wall-bounded flows using a linearized Navier-Stokes equations based model (linear model). We consider two separate modelling questions: (1) can a linear model-based estimator be used to estimate instantaneous and statistical features of these coherent structures and (2) can we use the model to understand the effect of stratification on these structures. In both cases, the trends obtained from the linear model are compared to those obtained from Direct Numerical Simulations (DNSs). We find that the linear model is able to capture the pertinent features of these coherent large-scale structures observed in DNS.

Speaker Bio: Anagha Madhusudanan is a DST-INSPIRE Faculty Fellow at the Indian Institute of Science (IISc), Bangalore. Her expertise includes fluid mechanics, dynamical systems, and nonlinear dynamics, with a focus on chaos theory and computational mathematics.