Grant: Discovery Grants Program - Individual

Vortices - regions of strong rotation - are often referred to as the 'sinews and muscle of fluid motions' for the very fact that they are responsible for the transport of mass and momentum. Furthermore, the study of vorticity production, reorientation and annihilation are ubiquitous to a broad range of unsteady aerodynamic, hydrodynamic and hemodynamic problems found both in nature and engineering. Whether at the small scales of flapping flight or at large scales of stall on wind-turbine blades, understanding how vorticity is generated near a body and reoriented into the wake is critical towards optimization and flow control in such systems. Fortunately, due to current advances in camera, laser and processing capabilities, new methodologies in time-resolved, volumetric imaging are currently being introduced. These new methods are referred to as 'Shake-The-Box' (STB) or Tomographic Particle Tracking Velocimetry (Tomo-PTV), and are slated to break down long-standing barriers in lab- and field-based experimentation. Unlike existing Eulerian-based imaging techniques such as Tomographic Particle Image Velocimetry (Tomo-PIV), these new Lagrangian approaches provide detailed Lagrangian tracking information (long pathlines) at ultra-high seeding densities, on the order of 100,000 tracked particles at any given time step. This new approach opens up a whole new gamut of analysis techniques from pressure-field extraction near steady and moving bodies to direct Lagrangian Coherent Structure (LCS) identification in wakes. Since the development of numerical modelling approaches for complex flows demands high-quality experimentation for their validation and calibration, such new Lagrangian experimental techniques are expected to provide much needed insight into these elusive problems. Examples of such challenging cases include: high Reynolds number (turbulent) flows with a large range of temporal and spatial scales; unsteady aerodynamic and hydrodynamic interactions with structures; multiphase and transitional flows such as are found in the heart; and gust characterization in the atmosphere. The proposed research program will explore the use of these new Lagrangian-based measurement techniques and their associated post-processing strategies as a means to offer insight into the underlying physics of such flows. The proposal will begin by describing how the implementation of Tomo-PTV measurements is likely to shape the direction we take when analyzing these problems. In particular, we will look at how new formulations for networking tracked particles and their acceleration content will enable extraction of flow features such as pressure. With vorticity, we will investigate how measurements near unsteady bodies will provide insight into vorticity production and its reorientation in the wake, thus identifying possible new avenues for flow control and optimization.