Luís Mendes will defend his PhD thesis, "Real-Time Optical Flow Velocimetry for Natural and Built Environments," supervised by professor Alexandre Bernardino (Department of Electrical and Computer Engineering), professor Rui Ferreira, and professor Ana Ricardo (Department of Civil Engineering), on December 17th at 2:00 pm.

Room: PA-3 Alameda Campus;

Abstract: This thesis delves into the integration of optical flow (OpF) methods within Particle Image Velocimetry (PIV) applications, presenting an innovative analysis and benchmarking of novel OpF combinations. Specifically, it explores the synergy of Liu-Shen with Lucas-Kanade and Liu-Shen with Färneback. The study revisits the Lucas-Kanade and Färneback OpF methods, traditionally rooted in computer vision, and introduces the latter to fluid mechanics applications, a domain where it has been previously overlooked. A novel hybrid PIV approach, combining Liu-Shen with Lucas-Kanade, is assessed for its efficacy in turbulence information retrieval and enhancement of overall PIV performance. The research is complemented by the release of several open-source software tools to the public domain, including a synthetic PIV image generator, a comprehensive suite of OpF method reference implementations, and QuickLabPIV-ng—an efficient Aparapi/OpenCL implementation equipped with a Graphical User Interface(GUI) in Java. Additionally, an economical, portable PIV LED lighting unit is tested, that was created from scracth, promoting the early adoption of PIV technology in academic settings in tandem with QuickLabPIV-ng software. The OpF and hybrid PIV methodologies undergo rigorous benchmarking against both synthetic PIV image databases with established ground truth and real PIV image databases exhibiting varied quality and characteristics. The performance of these methods is meticulously evaluated across different flow types, considering the specific characteristics of PIV images to optimize method efficacy. The findings suggest that the hybrid PIV-OpF method enhances spatial resolution and augments the capacity of PIV to yield data suitable for fine-scale turbulence analysis, contingent upon the high quality of PIV images. Furthermore, the study posits OpF as a viable alternative to conventional PIV techniques. It also delineates critical flow regions and image conditions that influence method's accuracies.