“Applications in Biological and Bio-inspired Flows”
Dr. Danesh Tafti, Virginia Tech
There is much to be learnt from and understood about flows in biological systems. The seminar will treat two topics in the realm of biological flows: that related to the physiology of blood flow in stented coronary arteries, and the other related to the complex flow dynamics employed by birds and insects to fly.
Cardiovascular diseases are the number one cause of death in the world. The most common treatment of occlusive coronary artery diseases is the use of stents. Stent design profoundly influences the post-procedural hemodynamic and solid mechanical environment of the stented artery. Despite stents’ wide acceptance, the incidence of late restenosis is still high and it is most prevalent at the proximal and distal ends of the stent. In this work, we focus our investigation on the localized hemodynamic effects of compliance mismatch due to the presence of a stent in an artery and its effect on key hemodynamic parameters. It is shown through coupled fluid-structure interaction between the pulsatile flow and the stented artery that a pressure gradient increase at the ends of the stent creates additional vorticity at the wall resulting in an increase in the wall shear stress, which is known to cause an endothelial response that might lead to restenosis.
The interest in bird and insect flight is motivated by the need to build micro-air vehicles (MAVs) for surveillance and reconnaissance missions to enhance our war-fighting capability. The envisioned operational envelope of micro-air vehicles falls within that used by birds and insects, where conventional fixed-wing configurations are not only inefficient but fail to perform many of the functional tasks required of a MAV. Birds and insects use flapping wings to generate both lift and thrust. In this study we carry out fundamental studies on the unsteady aerodynamics that produce lift and thrust in a flapping wing. It is shown that to first order, the formation and longevity of the leading edge vortex (LEV) is a key ingredient in lift and thrust generation by a flapping wing. The manipulation of the LEV structure by wing kinematics, membrane wing flexibility and wind gusts is investigated in detail. Finally, some future potential research directions will be identified.
Danesh Tafti obtained his PhD in mechanical engineering at Penn State University in 1989. From 1989 to 1991 he served as a postdoc in the mechanical and industrial engineering at the University of Illinois at Urbana-Champaign. He then joined the National Center for Supercomputing applications there, where he held positions of research scientist, senior research scientist and associate director. At NCSA his research focused on developing novel programming paradigms on emerging high-performance computing architectures for applications to computational fluid dynamics and turbulent flow simulations. He joined the Mechanical Engineering Department at Virginia Tech in January 2002 as an associate professor and directs the High Performance Computational Fluid-Thermal Science and Engineering Lab. He was promoted to the rank of professor in 2008 and holds the William S. Cross Endowed Professorship in Engineering. His research interests are in high-end, multiscale, multiphysics simulations of single and multiphase systems in the broad areas of propulsion (solid-rockets, gas turbines for power and propulsion, and MAVs), energy (coal, biomass, wind and nuclear systems) and biomedical (cardiovascular) flows. He has over 150 peer-reviewed publications to his credit and has given several invited and keynote lectures at national and international conferences.