3-Dimensional Diffusion Flame in Microgravity (Hertzberg, Linne,
One approach to understanding turbulent flames is to study the response of laminar flames to specific perturbations. However, buoyancy effects can mask the flame response at low and transitional Reynolds numbers.
Vertical flame splits in response to high amplitude axial forcing; inverted flame does not.
This study applies active (periodic velocity perturbations) and passive (non-circular fuel jet cross-section) forcing to laminar and transitional flames in a microgravity environment. Flow visualization and particle tracking is performed in NASA's 2.2 second drop tower in addition to normal gravity studies. (National Aeronautics and Space Administration)
control of a planar jet (Peacock, Bradley,
This project is a combined experimental and numerical study of the transition to turbulence in a planar jet under the influence of micro-actuators. The jet first becomes unstable to two different kinds of periodic disturbance and we are initially investigating the ability of the micro-actuators to control this low-dimensional behaviour. Thereafter, we will consider controlling the mixing properties of the jet through different types of forcing (eg, quasiperiodic, chaotic).
Unforced jet, MEMS flaps present Forced jet.
Fluid Mechanics of Ventricular Filling (Shandas, Hertzberg).
As the mitral valve of the heart opens and flow from the left atrium into the ventricle begins, there is evidence that a vortex ring is formed. This ring is believed to be the primary mechanism which allows several important processes to take place: fluid must be efficiently transported into the left ventricle with a minimum of shear, while avoiding impingement against the apical wall, and thereby avoiding any resulting endothelial or hemolytic damage; the kinetic energy present in the incoming mitral flow must be smoothly translated to pressure energy; and a complete exchange of fluid in the ventricle must occur. Characterization of this vortex ring is expected to lead to improved diagnosis of diastolic dysfunction, which is considered to be one of the most accurate indicators of overall cardiac health. A study of the effects of non-circular orifice shape, vortex-wall interaction and double-peaked velocity time history on ventricular flow is in progress. The images below show differences in vortex structure due to a rectangular versus a trianglular velocity time history. (Whitaker Foundation)
Pulse Pressure Propagation (Shandas, Weinberg, Hertzberg).
A non-invasive ultrasound technique is being developed for determination of pulmonary vascular resistance based on a two-point correlation analysis of the pulse pressure wave propagation within an elastic artery.
Cough-Generated Infectious Aerosols (Miller, Fenelly, Hertzberg).
A number of diseases are transmitted by infectious aerosols generated by coughing. An analysis of coughing frequency and strength, as well as particulate size distribution and flow field will provide information needed to simulate coughs as pulsatile, particle-laden flows. This information can then be used in studies of disease transmission to determine infectivity risk and to develop realistic recommendations for protecting health care workers exposed to infectious aerosols.