Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session GH: Experimental Techniques: General I |
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Chair: Minami Yoda, Georgia Tech Room: Hilton Chicago Williford B |
Monday, November 21, 2005 10:34AM - 10:47AM |
GH.00001: Full-scale high-speed ``Edgerton'' retroreflective shadowgraphy of gunshots Gary Settles Almost 1/2 century ago, H. E. ``Doc'' Edgerton demonstrated a simple and elegant direct-shadowgraph technique for imaging large-scale events like explosions and gunshots. Only a retroreflective screen, flashlamp illumination, and an ordinary view camera were required. Retroreflective shadowgraphy has seen occasional use since then, but its unique combination of large scale, simplicity and portability has barely been tapped. It functions well in environments hostile to most optical diagnostics, such as full-scale outdoor daylight ballistics and explosives testing. Here, shadowgrams cast upon a 2.4 m square retroreflective screen are imaged by a Photron Fastcam APX-RS digital camera that is capable of megapixel image resolution at 3000 frames/sec up to 250,000 frames/sec at lower resolution. Microsecond frame exposures are used to examine the external ballistics of several firearms, including a high-powered rifle, an AK-47 submachine gun, and several pistols and revolvers. Muzzle blast phenomena and the mechanism of gunpowder residue deposition on the shooter's hands are clearly visualized. In particular, observing the firing of a pistol with and without a silencer (suppressor) suggests that some of the muzzle blast energy is converted by the silencer into supersonic jet noise. [Preview Abstract] |
Monday, November 21, 2005 10:47AM - 11:00AM |
GH.00002: High-speed flow visualization with a new digital video camera Jason Volpe, Gary Settles Scientific photography opened new vistas upon high-speed physics in the previous century. Now, high-speed digital cameras are becoming available to replace the older photographic technology with similar speed, resolution, and light sensitivity but vastly better utility and user-friendliness. Here we apply a Photron Fastcam APX-RS digital camera that is capable of megapixel image resolution at 3000 frames/sec up to 250,000 frames/sec at lower resolution. Frame exposure is separately adjustable down to 1 microsecond. Several of the ``icons'' of high-speed flow visualization are repeated here, including firecracker and gram-range explosions, popping a champagne cork, vortex rings, shock emergence from a shock tube, the splash of a milk drop, and the burst of a toy balloon. Many of these visualizations utilize traditional schlieren or shadowgraph optics to show shock wave propagation. Still frames and brief movies will be shown. [Preview Abstract] |
Monday, November 21, 2005 11:00AM - 11:13AM |
GH.00003: Design, Construction and Operation of a Light Gas Gun John Borg, Thomas Downs In order to conduct Richtmyer-Meshkov instability experiments in shock accelerated thin liquid sheets, a light gas gun was designed and constructed at Marquette University. This paper contains the basic predictions and construction techniques utilized in the design and operation of a double diaphragm light gas gun. The compressed air gas gun is used to accelerate a nylon projectile up to a velocity of 300 m/s. Pretest simulations were performed using two different hydrodynamic computational codes in order to simulate the inboard gas dynamics and projectile velocity. These simulations are compared with post test projectile velocity data. The simulations compare favorably to the data, including the one-dimensional calculations which do not account for frictional losses or diameter changes between the breech and barrel. Finally, both the computational simulations and the experimental measurements are compared to simple analytical predictions of the projectile velocity. [Preview Abstract] |
Monday, November 21, 2005 11:13AM - 11:26AM |
GH.00004: Development of Pressure Sensitive Molecular Film for Micro Devices Yu Matsuda, Hideo Mori, Tomohide Niimi, Hiroyuki Uenishi, Madoka Hirako The pressure-sensitive paint (PSP) has potential as a diagnostic tool for pressure measurement in the high Knudsen number regime because it works as a so-called ``molecular sensor.'' However, application of the PSP to micro devices has never been reported because the conventional PSP is too thick owing to the use of polymer binder. In this study, we have adopted Langmuir-Blodgett (LB) technique to fabricate pressure sensitive molecular films (PSMFs) using Pd(II) Octaethylporphine (PdOEP) and Pd(II) Mesoporphyrin IX (PdMP), and have tested these PSMFs to evaluate the feasibility of the pressure measurement around the micro devices. It is clarified that the PSMF composed of PdMP has higher sensitivity than that of PdOEP. Since it is also considered that the sensitivity of PSMFs can be increased by introducing arachidic acid as the spacer molecules to prevent the aggregation of luminescent molecules, we have produced PSMFs with several molar ratio of PdMP to arachidic acid. At the most suitable ratio, the PSMF has sufficient sensitivity in the low pressure region with high Knudsen number, even if the amount of the luminescent molecules in the PSMF layer is smaller than that in conventional PSPs. This indicates that the PSMF is feasible to measure the pressure in high Knudsen number flows such as micro flows. [Preview Abstract] |
Monday, November 21, 2005 11:26AM - 11:39AM |
GH.00005: Refractive index matching using a diethyl phthalate/ ethanol solution Paul Miller, Kurt Danielson, Jean Hertzberg, Andy Slifka, Elizabeth Drexler, Galan Moody When studying internal fluid velocity fields of complex geometries such as \textit{in vitro }cardiovascular models, refractive index matching is critical for undistorted images. A diethyl phthalate (DEP) / ethanol mixture is a good choice of working fluid due to the high index of refraction, low viscosity, safety and low cost. The mixture can be tuned to the refractive index of borosilicate glasses, fused quartz and silicone elastomers. Silicone elastomers do not cloud in DEP/ethanol solutions and also tested negative for change in compliance after DEP exposure. Material compatibility tests showed that only specific formulations of ABS, acrylic, vinyl and PVC plastics are compatible. Measurements were made of index of refraction and viscosity of varied DEP/ ethanol solutions at a range of temperatures, and empirical models for viscosity and refractive index will be presented. [Preview Abstract] |
Monday, November 21, 2005 11:39AM - 11:52AM |
GH.00006: Investigation of the Photophysical Properties of (CdSe)ZnS Quantum Dots and Their Use as a Fluorescent Tracer for Thermofluid Diagnostics Hui Hu, Manoochehr Koochesfahani, Behshad Shafii, Preston Snee, Moungi Bawendi, Daniel Nocera Chemically synthesized semiconductor quantum dot (QD) nanoparticles can offer certain advantages for fluorescence imaging compared to other commonly-used dyes such as Fluorescein and Rhodamine B. The photophysical properties of (CdSe)ZnS QDs are presented in terms of their absorption and emission spectra, stability against photobleaching and temperature sensitivity under laser excitations at the wavelengths of 308nm, 488nm and 514.5nm. The application of QDs for thermal-fluid diagnostics is demonstrated by using them as fluorescent tracers to conduct flow visualization and concentration measurement in a pulsed jet flow, and temperature distribution mapping in a stratified flow. \newline [Preview Abstract] |
Monday, November 21, 2005 11:52AM - 12:05PM |
GH.00007: Imaging isothems in convecting viscous fluids. Anne Davaille, Valerie Vidal, Judith Vatteville, Angela Limare, Michael Le Bars, Damien Jurine, Catherine Carbonne, Gerard Bienfait In order to characterize thermal convection patterns in homogeneous and heterogeneous viscous fluids, we have developped a new technique using liquid crystals slurries which enables to image isotherms. When illuminated with white light, a liquid crystals slurry responds over a wide temperature range, and require a high-quality colour camera, and careful calibration and postprocessing to retrieve the temperature data from the images. In viscous fluids, such as sugar syrups or mixtures of salted water and cellulose, convective motions are slow (1 mm/hour to 5 mm/sec), temperature heterogeneities can reach 10-25\r{ }C, and experiments can run for several weeks. We therefore choose to visualize four different ``~isotherms~'', i.e. four temperature ranges as narrow as possible, by mixing four liquid crystal slurries in the experimental fluid, in the proportion of 0.1g/L each, and illuminating the solution with a laser sheet from a compact solid-state diode-pumped, laser, emitting a single-frequency green at 532 nm. Images were taken with a black and white CCD and the temperature precision reached 1{\%}. This technique can be used in combination with PIV to obtain also the velocity field and with fluoreceine markers to obtain the compositional field. [Preview Abstract] |
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