Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session T12: Experimental Techniques: Laser-Based Diagnostics (8:00am - 8:45am CST)Interactive On Demand
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T12.00001: Development and optimization of Optical-fiber-based Reflectance Probe (ORP) for liquid-film thickness measurement Kampei Yamaguchi, Yuki Mizushima Liquid-film flow is frequently encountered in the industrial field and is directly related to product safety, efficiency, and yield. Researchers use the conductivity method for measuring liquid-film thickness. However, it is hard to realize sufficient resolution in a real machine due to environmental disturbances such as high-temperature, high-pressure, and so on. Therefore, we propose an Optical-fiber Reflectance Probe (ORP) as a liquid-film thickness measurement method for practical use. ORP is a non-contact method that estimates the distance from its tip to the gas-liquid interface (liquid film thickness $L)$ by measuring the reflected light from the interface (Glare light). First, we examined the relationship between $L$ and Glare light intensity $I$ detected by the ORP, empirically. Second, we simulated the experiments with our original 3D Ray Tracing method. It suggests that the fiber-types determine the relationship between $L$ and $I$. Finally, we will design some types of ORP for optimization according to target liquid-film thickness and flow condition. [Preview Abstract] |
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T12.00002: Direct measurements of vorticity with phosphorescence anisotropy in a free turbulent jet Markus Johann Schmidt, Thomas Roesgen The utilization of phosphorescence anisotropy has recently been proposed for the direct measurement of vorticity. Dye-stained spherical nanoparticles in a fluid are illuminated with polarized light providing an orientation-sensitive excitation mechanism. The phosphorescence emission is polarized as well, and the observable polarization anisotropy can be related to the rotation of the particles during the phosphorescence lifetime. Integrating measurements were performed at first to overcome the low phosphorescence quantum yield. The signals could be acquired with a cooled CCD camera, integrating the signal over several pulsed laser excitations to analyze mean vorticity contributions. As an example for time resolved flow analysis, a free turbulent jet at Re 3000 was then investigated with an intensified sCMOS camera recording single shot signals, enabling statistical analysis of the flow regime with respect to vorticity. The talk will focus on an introduction of the measurement principle, followed by a presentation of single shot flow measurements and their analysis. [Preview Abstract] |
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T12.00003: Tomographic PIV in the 48'' Diameter Garfield Thomas Water Tunnel To Measure the Volumetric Velocity Field of a Propeller Wake Adam Nickels, Jeff Harris Tomo-PIV measurements of a propeller wake in the Garfield Thomas Water Tunnel are presented. Performing such measurements in this historic tunnel presents a number of challenges, especially limited optical access with thick windows required to withstand the high static pressures necessary to run at high flow speed. As a demonstration, the simplest optical setup was used. The generic propeller spun at 625 rpm with a thrust of up to 30lbs. The measurements were acquired at 2500 fps using four Phantom v1212 cameras in a linear arrangement and a Photonics DM-50 to illuminate the volume. The measurement volume was up to 5.5x7x1.6 inches (140x180x40mm). Data were processing using tomographic algorithms in LaVision's DaVis 10.0.4 with voxel size of 56 cubic pixels and 51x56x20 vector resolution. Results show that volumetric velocity measurements are possible in relatively large volumes. With a propeller diameter of 10 inches, much of the propeller wake was measured at once with finely resolved time evolution of the flow structures. Given the 4-inch thick acrylic windows, resolving a sizeable volume in the center of the 48-inch water tunnel proved a surmountable challenge. [Preview Abstract] |
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T12.00004: Real-Time Particle Monitoring Using Digital Inline Holography Rafael Grazzini Placucci, Siyao Shao, Buyu Guo, Jiarong Hong The analysis of particle concentration, size and shape distribution is critical in many engineering applications and fundamental research, including spray coating, pollutant monitoring, cellular identification, and sorting, etc. Unlike conventional techniques, such as laser diffraction and phase Doppler analysis, the emerging digital inline holography (DIH) technique could provide imaging-based quantification of particle size and shape using a simple and inexpensive setup without knowledge of particle characteristics. Nevertheless, DIH is computationally expensive. In this presentation, we introduce a novel mobile DIH device for high-precision \textit{in situ }characterization of particles. Compared to conventional DIH, the proposed system leverages machine-learning, multi-threading programming, and embedded GPU computing to achieve real-time hologram acquisition and processing. Measurements of spray size distribution obtained from a consumer-grade nebulizer demonstrate high measurement fidelity and significant improvement in the speed of particle characterization compared to previous DIH systems. We expect this technique can be widely employed in spray analysis and other particle analysis tasks, such as airborne pollutant monitoring and biotic particle analysis. [Preview Abstract] |
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T12.00005: Temperature imaging in fluid flows with sub-\textdegree C precision using Bi-doped phosphor particles and a single low-frame rate camera Benoit Fond, Christopher Abram, Irin Wilson Panjikkaran, Simon Nnalue Ogugua Study of coupled fluid mechanics, heat transfer and chemical processes require sensitive temperature measurements that reveal the structure and dynamics of the fluid flow. Temperature imaging using the laser-induced photoluminescence of inorganic phosphor particles is an attractive approach as it combines both the high resolution of laser induced fluorescence techniques and particle tracers that are inert, independent of the fluid chemical composition and pressure, and suitable for joint velocity measurement. Until now the temperature precision has been limited to a few \textdegree C due to the low temperature sensitivity of measurement approach and phosphor. In this study, we synthesised ScVO$_{\mathrm{4}}$:Bi$^{\mathrm{3+}}$ particles whose \textmu s luminescence lifetime is very sensitive temperature and can be exploited using a single low frame rate interline transfer camera to perform rapid-lifetime temperature imaging. The ratio of both frames yields a temperature sensitivity of 3-6{\%}/K over the 20-60\textdegree C range. A demonstration thermal mixing experiment indicates a single shot single pixel temperature precision better than \textpm 0.4\textdegree C at a resolution of 400 \textmu m. This simple single-camera approach is ideally suited to the temporally and spatially resolved study of complex thermal convection phenomena. [Preview Abstract] |
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T12.00006: Optical Measurements of Ice-Induced Strain Effects on Single Layer Graphene William Scougale, Subash Kattel, Joseph Murphy, Samuel Pasco, John Ackerman, Vladimir Alvarado, William Rice A deep understanding of material interfaces remains challenging due to the difficulty in probing their limited spatial extents and complex properties. In particular, the material interface with ice is scientifically intriguing and economically valuable, but poorly understood. Measuring the properties of ice adhesion, crystallography, and strain are important for icing physics, as well as understanding real-world behaviors and designing icephobic coatings. In this work, we use Raman spectroscopy to measure the strain created by ice on quartz-mounted single-layer graphene (SLG). We observe a shift of -2 cm$^{-1}$ in the 2D peak of SLG upon ice formation from 0 to -20$^{\circ}$C, which we attribute to the mismatch between SLG and ice. Additionally, spatial mapping of the SLG surface reveals a distinct 2 cm$^{-1}$ downward shift in the SLG 2D peak in regions where ice has formed. This ice-created change in the SLG Raman spectrum is indefinitely maintained after ice removal and is only restored when the SLG is heated above room temperature. Finally, we study different purities of distilled water to isolate strain and water-SLG charge transfer effects. These results help demonstrate the applicability of 2D materials as interfacial strain probes of ice and other critical materials. [Preview Abstract] |
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