Understanding turbulence measurements in complex flows
Dr. Sean Bailey
1:00 PM on 2008-03-25
227 Akerman Hall
Performing and interpreting measurements in complex turbulent flows is still a challenging task despite continual advances in fluid flow measurement technology since the inception of hot-wire anemometry in the early 20th century. The correct interpretation of experiments is crucial to elucidating the physical mechanisms that control turbulent transport, and to developing improved models for turbulence. I will illustrate these difficulties by describing three particular experiments. In each case a different approach was required to gain insight into the flow phenomena under investigation. First, I will describe measurements of a wing-tip vortex that is wandering in free-stream turbulence. In this case, two point, three-component velocity measurements were used to resolve the properties of a wing tip vortex undergoing unsteady motion and thereby determine the relationship between the rate of vortex decay and the free-stream turbulence. Second, I will describe measurements of the azimuthal length scales of large and very large scale motions in turbulent pipe flows. Here, cross-spectral analysis was required to separate the contributions of two distinct motions to the azimuthal correlations. Finally, I will introduce the problem of spatial resolution in hot-wire measurements of very high Reynolds number wall flows and will describe current efforts to develop a new nano-scale hot-wire probe.