SGER: DESIGNED VORTICES AND HYBRID VIRTUAL-PHYSICAL EXPERIMENTS FOR VORTEX DYNAMICS RESEARCH

Cornell University, Ithaca NY

Investigators

Abstract

CBET-0813835 Williamson This exploratory research project will bring the PI's work on fundamental vortex dynamics, instabilities and the onset of turbulence to study propulsion and energy extraction from unsteady controlled motion of bodies. The PI will also study vortex-induced vibration, and dynamics of flying objects, as well as freely rising and falling bodies. Two exploratory research investigations that should deliver quite powerful and general tools are: firstly, an efficient method to generate multiple vortices, possibly in the presence of solid bodies or a wall; and secondly, building a "Virtual Unsteady Dynamics Facility." Concerning the first approach, rather than observe vorticity distributions after the fact, the PI will determine how to move a body, relative to a fluid, to deliver a pre-determined vortex configuration - in short to actually design a vortex configuration. A key to this idea is to devise a model of the vortex formation from sharp-edged bodies. The approach involves translating a vertical airfoil in a horizontal plane (like one uses a giant XY plotter), employing the Cornell computer-controlled XY Towing Tank. An immediate application, where this approach is urgently needed is that of vortex configurations applicable to aircraft trailing vortex wakes, including counter-rotating or co-rotating vortex interactions, and their interaction with the ground. The second approach involves development of a Virtual Unsteady Dynamics Facility, which will allow a body in the fluid to move as though it were elastically-restrained; the structural stiffness, damping and mass are represented in software within a computer, while the fluid forces and moments on the body are those actually measured from the physical body. The motion of the body is computer-controlled by the towing tank carriage system, following the equations of motion represented in the software. The PI can experiment with freely rising and falling bodies by representing gravity as a horizontal force! Direct comparison can be made with some existing experiments studying free dynamics of spherical and cylindrical bodies. Flutter of falling bodies such as plates can be studied with a view to understanding tumbling and rocking modes in terms of the vortex dynamics and stall. The PI has involved 177 students in his research laboratories from 1990-2007, and his involvement with undergraduates, including minority undergraduates, will continue with this project. A large proportion of those undergraduates, whose experience has been in the PI's laboratories, have gone on to Masters and PhD degrees.