Energized mass and its application to airborne seeds and sensors

Abstract

Large-scale flow-tracking measurements require sizeable flow tracers for optical visibility, or the carrying of a sensor payload. As a result of the increased size and mass, the tracers experience an inertial lag, impacting flow fidelity and measurement accuracy, especially in unsteady flow conditions. This thesis approaches the tracer-lag problem through a physics-based modelling framework while also exploring biologically-inspired flow tracers and a non-optical flow-sensing system. For the latter, coupling a low-order correction with improved tracer flow fidelity has potential applications in distributed flow-sensing (non-optical) techniques. The studies in this thesis focus on the development of a novel modelling framework and its application to the gust-response of wind dispersed seeds and flow sensors with inertial measurement units (IMUs). First, the concept of energized mass is introduced and validated as a robust framework for modelling forces in separated flows. Second, the gust response of the milkweed seed, which achieves flight through drag-producing bristles, is characterized and the applicability of the energized-mass approach is examined. Finally, a proof of concept for a non-optical, IMU-based flow measurement tool is presented, enabled by the energized-mass-based model correction. When combined, these results contribute to the understanding and modelling of unsteady forces, while also providing a step towards improved large-scale flow measurements.