TrackAER: Volumetric Event-Based Particle Tracking Velocimetry in Real-Time
EMBARGOED UNTIL 2026-03-17
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Date
2023
Publication Type
Doctoral Thesis
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yes
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EMBARGOED UNTIL 2026-03-17
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Abstract
In experimental fluid mechanics, both the instant, intuitive visualization of a flow field and its accurate capture in quantified form are vital to study and fully understand the complex underlying physics. These two categories of techniques tend to be mutually exclusive due to the significant data overhead associated with existing quantitative flow visualization methods. As such, an open research objective is the development of a measurement system that enables the accurate reconstruction of time-resolved, three-dimensional flow fields, while delivering and rendering the information in real-time as the flow evolves. Addressing the issue, this thesis proposes a novel measurement system called TrackAER which employs multiple neuromorphic event cameras for real-time flow tracer tracking and online flow field reconstruction. The biologically inspired operation principle of said devices is fundamentally different from conventional frame-based cameras as they do not capture spatially dense, absolute intensity information at fixed time intervals. Instead, event cameras only sense local temporal contrast changes. As such, they generate an asynchronous stream of semantically condensed data corresponding to the visual signature of the moving tracers only, and with a data rate automatically adapted to the visual stimuli. A corresponding, asynchronous data processing pipeline is developed in this work, which exploits the characteristics of the event data stream for extremely fast processing such that tracking, photogrammetric reconstruction, and velocity estimation are carried out without noticeable temporal delay. The reconstructed flow fields are real-time visualized in the form of tracer path lines that are quantitatively labeled with additional information, such as the local flow speed. The interactive, virtual, and three-dimensional representation of the flow scene in the TrackAER software offers a high level of immersion. Targeted test volumes are at the industry-relevant cubic meter scale such that neutrally buoyant helium-filled soap bubbles become the flow tracers of choice. Investigations of both transient flow phenomena as well as continuous measurements with long durations are enabled. Short tests of only a few seconds suffice to capture the predominant structures in a flow, and the temporal accumulation of the tracer reconstructions yields a dense and detailed representation of the flow field under investigation. A diverse set of test cases successfully demonstrates the broad applicability and validity of the TrackAER system, indicating measurement accuracies in the sub-percent range, on par with or better than conventional pressure-probing.
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published
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Examiner : Rösgen, Thomas
Examiner : Delbruck, Tobi
Examiner : Willert, Christian E.
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ETH Zurich
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Subject
Aerodynamic testing; Wind tunnel; Event cameras; Real-time processing; 3D PTV; Time-resolved measurements; Flow diagnostics; Large-scale flow diagnostics; Aerospace; Automotive; Experimental fluid dynamics; Flow visualization; Quantitative flow visualization
Organisational unit
03479 - Rösgen, Thomas (emeritus) / Rösgen, Thomas (emeritus)