Dissecting the Flow Physics of Aeroelastic Oscillations and Vortex-Dominated Flows: Computational and Data-Driven Methods

Fluid flows interact with flexible and moving bodies in a wide range of natural and engineering applications. These problems are often characterized by highly non-linear flow physics due to the generation and shedding of several vortices, their interactions, and the forces they induce on surfaces within the flow. However, our current understanding of the force producing mechanisms in these flows and our ability to accurately quantify their influence remains limited. As a result, the dynamics of many such vortex-dominated problems involving fluid-structure interactions and unsteady aerodynamics are notoriously hard to predict. In this work, we use computational modeling in conjunction with data-driven techniques to analyze the flow physics of these problems. We particularly focus on the flow-induced oscillation of wings and cylindrical bluff-bodies at low Reynolds numbers. Using simulations based on a sharp-interface immersed boundary method, we demonstrate the large range of oscillation responses and parametric dependencies that these systems exhibit. We propose an energy-based tool to analyze, predict and control the non-linear, and often non-intuitive, oscillation responses observed. We show that ``energy maps'' identify all possible flow-induced oscillation response branches and bifurcations in a system, thus allowing their use in the prediction and control of pitching oscillations for wings interacting with incoming gusts. Furthermore, we also formulate and demonstrate a novel extension to Dynamic Mode Decomposition for the analysis of such flows involving moving boundaries. A second focus of this work is on disentangling the various mechanisms at play in the generation of loads on surfaces within vortex-dominated flows. To this end, we develop a force and moment partitioning method which allows us to rigorously quantify the influence of distinct physical mechanisms as well as individual flow features in force/moment production. This method is combined with data-driven techniques to estimate the influence of each individual vortex in a flow-field, while also tracking and categorizing these vortices as they evolve with the flow. We utilize these tools to reveal new insights into fundamental phenomena in aerodynamics and flow-induced oscillations -- such as the mechanisms that drive the flow-induced oscillation of cylinders and the production of lift during dynamic stall and on three-dimensional wings