Bulletin of the American Physical Society
60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007; Salt Lake City, Utah
Session BI: Experimental Techniques I |
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Chair: Jim Crafton, Innovative Scientific Solutions Room: Salt Palace Convention Center 250 C |
Sunday, November 18, 2007 10:34AM - 10:47AM |
BI.00001: Volumetric Three-Component Velocimetry Gang Pan, Daniel Bjorkquist, Daniel Troolin, Hai Zhang, Wing Lai We have developed and tested a novel 3D PIV system, Volumetric Three-Component Velocimetry (V3V), for instantaneous volumetric measurement of the three-dimensional velocity fields. The V3V system, which is based on the Digital Defocusing PIV (DDPIV) technique originally developed at CalTech, uses volume illumination and employs a unique 3D camera to capture two-frame double-exposure particle images at 7.5 fps in a 10x10x10 cm$^{3}$ volume. The captured images are processed by a fast reconstruction algorithm to obtain particle 3D positions. The positioning accuracy is about 10 um in XY and 40 um in Z based on the experiment results. A particle tracking method based on the expectation-maximization algorithm has been implemented to extract three-component velocity vectors. From each capture we can obtain 5000 $\sim $ 10000 particle velocity vectors in the measurement volume, and it takes only about 10 seconds to process each capture from the raw image to the final vector field. The capability of the V3V system has been assessed in various water flow measurement including a vortex ring flow and the flow past a wing in a water tunnel. [Preview Abstract] |
Sunday, November 18, 2007 10:47AM - 11:00AM |
BI.00002: Development of a Kilo-Hertz Particle Image Velocimetry System Using LED's Jim Crafton, Larry Goss, Jordie Estevadeordal PARTICLE SHADOW VELOCIMETRY (PSV) is a velocity measurement technique similar to PIV. PSV utilizes low-power pulsed light sources, such as an LED, to measure the displacement of seed particles in a flow. This is accomplished by imaging the extinction of light by the particles in the flow rather than the scattering, thus the power requirements of the lighting are significantly reduced. Data analysis involves cross-correlation of images at known time intervals to determine velocity. The use of LEDs' as a light source provides several advantages, among these are repetitive pulses in a single frame for particle tracking, the use of color to eliminate the need for cross-correlation cameras, and a significant reduction in equipment cost relative to lasers. Volumetric illumination eliminates the strong reflections from surfaces that often saturates the camera near the surface in traditional PIV thus allowing measurements to be made as close as 10-micrometers to a surface. This method is most applicable to liquid flows, near surfaces, and for small fields of view. Results are presented for several flows including kHz data in valves and artificial hearts. [Preview Abstract] |
Sunday, November 18, 2007 11:00AM - 11:13AM |
BI.00003: \textit{In Vivo} $\mu $PIV Measurements of Blood Flow in Small Vessels of a Rat Model. Timothy Wei, Nadine Conner, John Russell, Paul Legac Ongoing research at the University of Wisconsin Medical School is addressing the effects of perfusion of glottal tissue on voice production. Building on the approach developed by Gharib's group at CalTech for embryonic zebra fish, we have modified $\mu $PIV to measure flow in capillaries and small blood vessels in a live rat model. In lieu of seeding particles, the DPIV correlation algorithm tracks the motion of red blood cells moving through these vessels. The methodology will be presented along with a video sequence showing measurements made from muscle tissue laid nominally flat on a microscope stage. Challenges of measurements in three-dimensional geometries, $i.e.$ the throat, will be discussed. [Preview Abstract] |
Sunday, November 18, 2007 11:13AM - 11:26AM |
BI.00004: The spatial resolution of velocity and velocity gradient turbulence statistics measured with multi-sensor hot-wire probes P. Vukoslav\v{c}evi\'{c}, N. Beratlis, E. Balaras, J.M. Wallace A highly resolved turbulent channel flow DNS with $Re_{\tau}=180$ was used to investigate the effects of the spatial resolution of a twelve-sensor hot-wire probe on measurements of velocity and velocity gradient based statistics. Sensor array separations varying from $S^+=2$ to 12 (Kolmogorov lengths $\eta=1$ to 6 at $y^+=15$) have been examined, where the sensors were represented as points on the simulation grid. The effective velocity cooling each sensor was determined, and the sensor equations were then solved in response to the DNS flow field to obtain the velocity and velocity gradient components for two cases. These were: 1) an idealized probe where the influence of the velocity component tangential to the sensors and flow blockage by the presence of the probe are neglected and (2) a real probe, the calibration coefficients of which have been determined experimentally. The resolution effects on the statistics obtained from the ideal and real probes are quite similar. These effects are greatest for the $v$ velocity and $\omega_z$ vorticity components. For $S^+=8$ ($\eta=4$ at $y^+=15$), the rms peaks of these components are attenuated by about 8\% and 15\%, respectively. Their skewness and flatness factors are also strongly affected. PDFs and $k_x$ spectra of the velocity and vorticity components will be discussed to explain these effects. [Preview Abstract] |
Sunday, November 18, 2007 11:26AM - 11:39AM |
BI.00005: Comparative Measurements in G\"ortler Vortices Flow Using Split-Fiber and Hot-Wire Velocimetry Ladan Momayez, Guillaume Delacourt, Pascal Dupont, Hassan Peerhossaini We calibrated a Split-Fiber probe in a concave wall for measuring two-dimensional velocity in G\"ortler vortices flow. The subject of this paper is the relative merits of Split-Fiber and Hot-Wire measurement techniques in studies of G\"ortler vortices flow processes as typically encountered in control scenarios for technology applications. A comparison of the two diagnostic systems is made on the basis of simultaneous measurements or local mean velocities and root-mean-square values of velocity fluctuations. Longitudinal and vertical velocity fields in the concave boundary layer, at several streamwise stations was measured by Split-Fiber and wire anemometry. These results corroborate the conclusion made on the effects of perturbations wavelength and amplitude on the heat transfer enhancement by G\"ortler vortices. Where applicable, both measurement techniques yield comparable results, a finding, which is consistent with observations in visualization. [Preview Abstract] |
Sunday, November 18, 2007 11:39AM - 11:52AM |
BI.00006: Ultrafast Full-Field X-ray Imaging and its Applications in Fluid Dynamics. Kamel Fezzaa, Yujie Wang The x-ray beam afforded by third-generation synchrotrons, such as the Advanced Photon Source (APS), has unique properties: extremely high intensity, wide energy tunability, high coherence, and flexible lattice timing structure. To take full advantage of these properties, we are developing a novel x-ray research tool, involving ultrafast phase-enhanced full-field x-ray imaging, with both micrometer-spatial and sub-nanosecond temporal resolutions. Such capability has never been realized before, and will make tremendous impact on numerous fields, both scientifically and technologically. We will present some examples of our work, ranging from our first high-quality phase-enhanced radiographs through a few-millimeters-thick stainless steel fuel injector nozzle, where the exposure time was a few seconds, to our first successful use of a single bunch from the APS ring to take 150 ps snapshots of the internal structure of a high-speed fuel spray. We will present highlights from ongoing research such as droplets pinch-off, coalescence and collision. We will also show how velocity field distribution of dense liquid jets can readily be measured with this technique. [Preview Abstract] |
Sunday, November 18, 2007 11:52AM - 12:05PM |
BI.00007: Measurement by Digital Image Correlation of the topography of a liquid interface Frederic Moisy, Marc Rabaud, Kevin Salsac A non intrusive method to measure the instantaneous topography of a fluid interface with a resolution of 1~$\mu$m is presented. This method is based on the analysis of the deformation of a random pattern of points due to the refraction through the interface. The cross-correlation between an instantaneous image and a reference image obtained when the surface is flat allows for the reconstruction of the local fluid height. Movies of time-resolved circular waves created by the impact of a drop are analysed. Other applications for this method, such as fluid coating and wave turbulence, will be discussed. [Preview Abstract] |
Sunday, November 18, 2007 12:05PM - 12:18PM |
BI.00008: Using a Laser-Cantilever-Anemometer for two dimensional measurements in turbulent flows Michael Hoelling, Joachim Peinke We present an improved version of the Laser-Cantilever-Anemometer which allows for measurements in two dimensions. By replacing a one dimensional PSD (Photo Sensitive Detector) with a two dimensional one, additional information about the direction of the local flow can be determined. Measurements carried out with the improved Laser-Cantilever-Anemometer in comparison to X-wire measurements are presented. [Preview Abstract] |
Sunday, November 18, 2007 12:18PM - 12:31PM |
BI.00009: Flow Measurement of Liquid Metal Flow in Spallation Target Model of ADS by using Ultrasound. Hironari Obayashi, Kenji Kikuchi Measurement of Lead Bismuth Eutectic (LBE) flow by Ultrasonic Velocity Profiler (UVP) technique was successfully realized in the mockup loop of shield annular tube type spallation target, JLBL-2 (JAEA Lead-Bismuth Loop-2), for Accelerator Driven System (ADS) target test facility in J-PARC (Japan Proton Accelerator Research Complex). UVP is a powerful tool to measure an instantaneous space-time velocity profile especially on a velocity measurement of an opaque liquid flow, such as liquid metal. However, it has not yet been done well because both of its poor wetting property with stainless steel and of the difficulty in manufacturing probe at high temperature. At lower temperature, wetting of LBE to stainless steel that is a material of target loop is too poor. Therefore, the surface of the test section was treated by polishing, flatting and finally coating with nickel and solder. And we performed velocity measurement along the centerline of the loop and confirmed basic performance of the loop. It was found that there were periodical releases of eddy from the re-circulation region formed near the wall surface of the inner cylinder. We made then a measurement for non-parallel directions with the centerline and observed 3-dimensional structure of LBE flow configuration. [Preview Abstract] |
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