演讲人： Tianshu Liu
题 目： Flow Structures Extracted from Visualization Images: Vector Fields and Topology
时 间： 201 8 年 6月 29 日 10:00-11:00
地 点： 哈尔滨工业大学（深圳） ，A栋507
We live in the fascinating world of fluids (e.g. air and water). Complex flows are observable through suitable visualizations in the natural environment and laboratory experiments. In this presentation, a unified theoretical framework is described for global flow diagnostics based on various flow visualizations to extract high-resolution velocity and skin-friction vector fields. Based on the projection of relevant transport equations from the 3D object space to the 2D image plane for important flow visualizations, a generic mathematical form of the projected motion equations is induced and further written as a physics-based optical flow equation. The variational formulation is given for solving the optical flow equation as an inverse problem. Examples are discussed to illustrate the applications of this method focusing on the topological aspects of extracted vector fields, particularly for spacecraft images of the Great Red Spot (the GRS) on Jupiter and Saturn’s north polar vortex. Furthermore, global quantitative skin-friction diagnostics in complex separated flows are discussed based on surface flow visualizations.
Tianshu Liu is a professor and the director of Applied Aerodynamics Laboratory at Western Michigan University (Kalamazoo, Michigan). He received a Ph.D. in aeronautics and astronautics from Purdue University (West Lafayette, Indiana) in 1996. He was a research scientist at NASA Langley Research Center (Hampton, Virginia) in 1999-2004. His research areas cover experimental and applied aerodynamics, and theoretical aerodynamics models. In particular, he has contributed to image-based aerodynamic measurement techniques for various physical quantities such as surface pressure, temperature/heat-transfer, skin friction, velocity fields, aeroelastic deformation and distributed and integrated forces. Other topics include videogrammetry and vision for aerospace applications, flow control, flapping flight, flight vehicle design, transition and turbulence, flight tests, and bias error theory.