Spring 2019 - Seminar Series
Dr. Qianhong Wu, Associate Professor, Villanova University
On the Lessons Learned from the Biological Systems for Soft Lubrication and Squeeze Damping
Dr. Qianhong Wu
Associate Professor, Department of Mechanical Engineering, Villanova University
Abstract
In this talk, I will apply lessons learned from the exquisite design of biological systems to examine two problems in fluid mechanics, soft lubrication and transient squeeze damping. Biological scientists have wondered, since the motion of red cells was first observed in capillaries, how a red cell, with an 8µm diameter, can move with so little friction in tightly fitting microvessels, only 5-6 µm in diameter, and survive 105 passages through microcirculation during a typical lifetime of 120 days without being damaged or undergoing hemolysis. This mystery has been attributed to the dramatically enhanced hydrodynamic lifting force generated inside the endothelial glycocalyx layer (EGL), a soft porous layer that covers the inner surfaces of our capillaries, as a red blood cell glides over it. We have performed a systematic, experimental and theoretical approach to examine the lift generation inside a compressible porous media. The fundamental physics and its diverse applications, from red cells moving in a tightly fitting capillary, to human skiing or snowboarding, to the classical lubrication applications, will be reported in the first part of the talk. The second part of the talk is related to our recent study about the mechanism of concussive and sub-concussive brain injuries. When a head is exposed to sudden external impacts, the flow of the cerebrospinal fluid (CSF) in the subarachnoid space (SAS) is a typical transient squeeze damping process, in which the convective fluid acceleration is very small due to the small Reynolds number; while the local acceleration of the fluid is not negligible due to the small Strouhal number. We have developed a comprehensive experimental, analytical and numerical approach to examine a fast developing flow in a thin fluid gap. Excellent agreement was obtained between the theoretical predictions and the experiment data. The study presented herein, from soft lubrication to transient squeeze damping, will have a very broad impact in both biological and industrial applications.
About the Speaker
Dr. Qianhong Wu is an Associate Professor of Mechanical Engineering at Villanova University. He is the founding director of Villanova Cellular Biomechanics and Sports Science Laboratory (CBMSS), and the director of the Mechanical Engineering Graduate Programs. Dr. Wu received his B.S. in Power Engineering from Huazhong University of Science and Technology (HUST), and M.S. in Electrical Engineering from the Institute of Electrical Engineering, The Chinese Academy of Sciences. He received his Ph.D. in Mechanical and Biomedical Engineering from The City College of The City University of New York in May, 2005, and subsequently joined the faculty of Mechanical Engineering at Villanova University. He was promoted to an Associate Professor with tenure in May 2011. Dr. Wu applies fundamental principles of fluid dynamics to the bio and bio-inspired applications. His research interests include porous medial flow, fluid dynamic and transport aspects of biological systems, cardiovascular engineering, brain biomechanics, cellular mechanisms for mechanotransduction, bone fluid flow, hemodynamics, sports biomechanics, and soft/super lubrication. These research projects have been supported by the National Science Foundation (NSF) and the Office of Naval Research (ONR). He has published extensively on these topics and been widely reported in Physical Review Letters®, Science®, Nature®, Scientific American®, PhysicsWeb®, etc.
Villanova University is a private research university, located in the Philadelphia suburbs of USA. With a strong and growing research reputation, Villanova is ranked by U.S. News & World Report the 49th best National University.