Fluid Projects

2 posts

Fluid motion estimation

Approach one: Variational optical flowIntroductionIn this project, we propose a novel optical flow formulation for estimating two-dimensional velocity fields from an image sequence depicting the evolution of a passive scalar transported by a fluid flow. This motion estimator relies on a stochastic representation of the flow allowing to incorporate naturally a notion of uncertainty in the flow measurement. The Eulerian fluid flow velocity field is decomposed into two components: a large-scale motion field and a small-scale uncertainty component. We define the small-scale component as a random field. Subsequently, the data term of the optical flow formulation is based on a stochastic transport equation, derived from the formalism under location uncertainty proposed in Mémin (2014) and Resseguier et al. (2017a). In addition, a specific regularization term built from the assumption of constant kinetic energy involves the very same diffusion tensor as the one appearing in the data transport term. Opposite to the classical motion estimators, this enables us to devise an optical flow method dedicated to fluid flows in which the regularization parameter has now a clear physical interpretation and can be easily estimated. Experimental evaluations are presented on both synthetic and real-world image sequences. Results and comparisons indicate a very good performance of the proposed formulation for turbulent flow motion estimation.   

Observation and motion reconstruction of flapping flight

IntroductionThis project mainly studies on the observation and motion parameters reconstruction of flapping flight, the stability analysis of insects hovering, and the flapping mechanisms design for the PIV experiments, aiming to improve the existing hull reconstruction and pose estimation algorithms, propose the analysis method of insect hovering under the active control under varying flapping frequency, and design flapping mechanisms with multiple freedoms for PIV experiments to implement more fined motion. As for hull reconstruction and pose estimation, the project reconstruct the hull of insect under the assumption that the insect body is rigid and its section is elliptical with the data of body radius, centerline and the wing outline. As for the experimental flapping motion system design, this project analyzes the design principles and keeps the Reynolds number and Strouhal number same in the real and experimental environment respectively, and describes how to the design bee-like and dragonfly-like flapping mechanisms and how the mechanisms are driven.Paper1.Y. Huang, J. Liang and C. Xu. Sability of the flapping-wing vehicle near hovering under active control by varying flapping frequency [C]. The Chinese Congress of Automation 2017, Jinan, Shandong, China, October 21-22, 2017.