Signatures of Chaos: A study in predictability of flows

Abstract

This work explores predictability in atmospheric flows. A study on forecasting is conducted in the Lorenz [1963] model using several Data Assimilation techniques. Methods of statistically combining model forecasts with observations for prediction are tested for their performance, which readily extend to higher dimensional systems and are oft encountered in Numerical Weather Prediction. Next, predictability in resolved three dimensional turbulence is investigated using high resolution flow simulations that provide an exciting avenue for forecasting or coupling with large scale circulation models. The Dutch Atmospheric Large Eddy Simulation (DALES) is adapted to study the evolution of perturbations in LES and DNS of a dry convective boundary layer. The effects of parameters like the perturbation magnitude, its wavenumber and location, and the flow Reynolds number are studied to find the governing modes of error growth. The implications on predictability in a system with a superposition of multiple scales are then discussed.Solid and Fluid MechanicsMechanical EngineeringMechanical, Maritime and Materials Engineerin