Fundamental vortex dynamics and interactions
The generation and evolution of coherent structures in fluid flows are important phenomena in a range of scientific and engineering applications. To investigate these features, we often use a method called the Lagrangian coherent structures.
In particular, we calculate the finite-time Lyapunov exponent field from measured or simulated velocity fields to reveal ridges of attraction or repulsion that shape the way the flow field evolves.
In some new projects, we are combining our established expertise in coherent structure identification and tracking with computationally fast numerical models of unsteady flow fields. This includes the discrete vortex method, which uses the generation and shedding of point vortices to approximate the evolution of unsteady flows. While such models are based on the inviscid flow assumption, they are able to illuminate fundamental concepts of unsteady fluid dynamics, which provides them with great utility for parametric investigations and practical modeling of vortex dominated flows.
Unsteady swimming and flying flows
One of the most natural inspirations for modern underwater vehicle technology is the locomotion of fish and aquatic mammals, which have proven to be examples of exceedingly efficient, maneuverable, or high-powered swimming.
By oscillating their fins and flukes, fish and aquatic mammals create complicated vortex-dominated wakes. We use both isolated fin models as well as more biomimetic multi-degree-of-freedom models in our experiments, and use techniques such as flow visualization by planar laser induced fluorescence (PLIF), stereoscopic particle image velocimetry (PIV). I am particularly interested in designing both active and passive control implementation on propulsive surfaces to enhance performance, and to better understand the interaction and potential benefits of multiple propulsive surfaces or varying motion profiles.
Unsteady wing aerodynamics
We also study the evolution of the 3D flow fields around delta wing planforms as models of aircraft encountering gusty conditions, or executing unsteady maneuvers. For example, at the high angles of attack at which a fighter aircraft would have to negotiate an aircraft carrier landing, the flow around its wings is highly susceptible to the turbulence created by the air's interaction with the ocean surface, and the ship itself. These disturbances create destabilizing forces and moments on the aircraft that can be extremely dangerous for pilots and crew.
Data visualization in extended reality
When studying these time-varying 3D flow field features, we are naturally hindered by visualizing them on 2D screens. In collaboration with colleagues from Architecture, Industrial Design, and Communications, we are exploring the potential of importing and interacting with our data in virtual or augmented reality as easily as opening the data files in our usual visualization software packages.