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 FI: Experimental Techniques II |
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Chair: Gary Settles, Pennsylvania State University Room: Salt Palace Convention Center 250 C |
Monday, November 19, 2007 8:00AM - 8:13AM |
FI.00001: A high-resolution tomograph for the study of thermal-fluids phenomena Timothy Upton, Dean Verhoeven A unique tomographic testbed having the ability to resolve small, three-dimensional structures has been constructed for the study of thermal-fluids phenomena. The twelve-view, high-resolution optical system employs a mirror array to deliver two projections or views to each of six cameras. The herein described tomograph provides a spatial resolution of 250 um for a field of view 32 mm in the horizontal direction by 64 mm in the vertical direction. To demonstrate the capabilities of the technique, fully three-dimensional measurements of the turbulent flame surface of a premixed, propane-air flame have been made. These whole-field measurements appear to be the first of their kind. The flow field with a mean speed of 11 m/s and rms turbulence of 0.36 m/s is frozen using a 10 us flash delivered by a uniformly-distributed, high-power flash ring. The light reflected from micron-sized oil droplets seeding the flow is acquired from twelve viewing directions. These projection measurements are used to reconstruct the flame reactants, providing the instantaneous flame surface in three dimensions. [Preview Abstract] |
Monday, November 19, 2007 8:13AM - 8:26AM |
FI.00002: Focusing-schlieren ``PIV'' for the measurement of 3-D turbulent flows Michael Lawson, Gary Settles, Leonard Weinstein Combining the particle imaging velocimetry (PIV) technique with schlieren optics allows flowfield measurements to be made in some cases without the need for particle seeding. Instead, turbulent eddies themselves play the role of seed particles in a transparent refractive flow. In our earlier work (Optics Lasers Engr. 44(3-4), 2006) a disadvantage of this method was found in that the measured eddy velocity is averaged across the flowfield due to the integrating propriety of conventional schlieren optics. Here, a focusing-schlieren system is implemented in order to remove that constraint and thus obtain ``planar'' velocity data in 3-D turbulent flows. This is demonstrated using an axisymmetric helium jet in air and a Mach 3 turbulent boundary layer in a supersonic wind tunnel. The results are promising, even though the simultaneous requirements of narrow depth-of-field and high schlieren sensitivity place severe constraints on the optics and are ultimately incompatible. [Preview Abstract] |
Monday, November 19, 2007 8:26AM - 8:39AM |
FI.00003: Schlieren-interferometry with a simple adjustable Wollaston-like prism Matthew Biss, Gary Settles, Simon Sanderson We demonstrate that a simple polycarbonate prism, here referred to as a Sanderson prism (Rev. Sci. Instr. 76(11), 2005), behaves under mechanical loading identically to the classical Wollaston birefringent prism. By varying the load, the Sanderson prism is adjustable up to the yield point of the polycarbonate, providing a typical range of beam divergence angles theta of 0-24 arcminutes. This range is thoroughly explored. The utility of the Sanderson prism for differential schlieren-interferometry at small theta and standard interferometry at large theta is demonstrated by using it in place of the knife-edge cutoff in large and small schlieren systems with laser or white-light illumination. A candle plume, the human thermal plume, and a small supersonic jet are used as example flows. Given the simplicity, adjustability, and low cost of the Sanderson prism, schlieren optics are easily converted to interferometry by applying it. Our exploration of differential interferometry at small theta and of white-light interferometry with the Sanderson prism extends the original work cited above. [Preview Abstract] |
Monday, November 19, 2007 8:39AM - 8:52AM |
FI.00004: On the limits of detection of a chemical vapor plume in air using the schlieren optical method Rory Bigger, Gary Settles A modest benchtop z-type schlieren optical system employing twin parabolic mirrors is characterized in terms of its sensitivity limit using the standard-lens method of calibration. A measurement by this method of the free-convection boundary layer on a heated vertical plate in air compares well with known theory. A mixing tube and oxygen sensor are then used to image laminar plumes of both helium and carbon dioxide in air at various mixture ratios, revealing a minimum value of the refractive-index gradient across the plume-air mixing boundary at its origin that is required for visibility. Thus the schlieren detection of a chemical vapor plume must depend upon the concentration of vapor in the air and the vapor refractive index. A range of chemicals is explored in order to determine the detectable concentration limit by this means. The results are discussed in terms of the possible use of schlieren optics to detect explosive vapor plumes in air. [Preview Abstract] |
Monday, November 19, 2007 8:52AM - 9:05AM |
FI.00005: Three-dimensional temperature reconstruction of steady and unsteady buoyant plume by background schlieren technique combined with computed tomography. Nobuyuki Fujisawa, Gen Sato The three-dimensional temperature fields of steady and unsteady buoyant plume issuing into a stagnant surroundings of water are measured by background schlieren technique combined with computed tomography. The measurement system consists of three CCD cameras, inline illuminations system and some optics, which allow three observations of refractive index field of the buoyant plume. The three-dimensional reconstruction technique is applied to the refractive index fields using multiplicative algebraic reconstruction technique for computed tomography. After the confirmation of the reconstruction accuracy with the thermocouple measurement, the experimental technique is applied to the three-dimensional temperature measurement of unsteady buoyant plume. The result reproduces well the unsteady three-dimensional behavior of the plume. [Preview Abstract] |
Monday, November 19, 2007 9:05AM - 9:18AM |
FI.00006: Temperature Measurement Technique Using Phosphorescence of Porphyrin Dyes Kentaro Kura, Satoshi Someya, Koji Okamoto LIF have been developed to measure the temperature, pH and the oxygen concentration in the fluid. However, the frequent excitation of the fluorescent dye causes the quenching effect. In addition, two color LIF should be applied in order to cancel the effect of non-uniform light intensity of excitation. The phosphor emitting the phosphorescence for a few milliseconds by an excitation was measured at the high time resolution, while the phosphorescence lifetime is the function of the temperature. As the phosphorescence dyes, PtTFPP and PdTFPP were tested. Those mixed with Coumarin30 were also demonstrated. These dyes were excited by a CW laser with the wavelength of 405nm. As the result, it was clarified to be able to measure the temperature using these dyes and this laser. Present study is the result of ``High speed three-dimensional direct measurement technology development for the evaluation of heat flux and flow of liquid metal'' entrusted to the University of Tokyo by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). [Preview Abstract] |
Monday, November 19, 2007 9:18AM - 9:31AM |
FI.00007: Measurement of Concentration Field in Miscible Displacement in a Hele-Shaw Cell by Means of Micro Electrode Takashi Ogawa, Yuichiro Nagatsu, Yoshihito Kato, Yutaka Tada Miscible displacement is a phenomenon a more-viscous fluid filled in a minute space is displaced by a less-viscous one which has the miscibility with the more-viscous one. In the miscible displacement in a Hele-Shaw cell, it is suggested the thickness of the less-viscous fluid layer in the cell's gap direction becomes thin near the front of the displacement. We call this shape `sheet structure'. We conducted experiment about the miscible displacement with a chemical reaction in a Hele-Shaw cell, and proposed a physical model of the reactive flow field in which the sheet structure plays important roles. The present study aims to examine whether the sheet structure is actually formed and the proposed model is appropriate, by the measurement using a micro electrode. The electrode was inserted in the cell through a hole in the cell's glass plate, and the concentration profile of the less-viscous fluid in the cell's gap direction was measured. When the no chemical reaction is included, the concentration profile has been obtained which suggests the presence of the sheet structure. [Preview Abstract] |
Monday, November 19, 2007 9:31AM - 9:44AM |
FI.00008: A forward-modeling approach for improved estimation of scalar concentration in image-based measurement Chris Tomkins A novel approach to estimation of concentration (and concentration gradients) from scalar images is presented. The approach involves the development of a forward model of the imaging process and a model of the concentration field; in general, the latter is optimized to create a simulated image that most closely matches the measured image. In the present work, the concentration field is represented by a simple pixellated model subject to Total Variation (TV) regularization, which is implemented as an additional term in the optimization cost function. The approach is used to analyze a series of artificial images and is shown to yield improved estimates of the concentration field and its derivatives by mitigating the effects of blur and noise. [Preview Abstract] |
Monday, November 19, 2007 9:44AM - 9:57AM |
FI.00009: Temperature Sensitive Particle for Velocity and Temperature Measurement. Satoshi Someya, Koji Okamoto, Masao Iida Phosphorescence and fluorescence are often applied to measure the temperature and the concentration of oxygen. The intensity and the lifetime of phosphor depend on the temperature and the oxygen concentration, due to the quenching effect of the phosphor. The present study clarified the effects of temperature on the lifetime of phosphorescence of Porphyrins, Ru(bpy)$_{3}^{2+}$ and the europium complex. The phosphorescence lifetime of oil solution / water solution / painted wall were measured with changing temperature and oxygen concentration. In addition, the optical property of the small particles incorporated with the europium complex was investigated in the oil/water. The lifetime was strongly affected by temperature. Then, the temperature sensitive particle (TSParticle) with metal complex was applied to measure temperature in Silicone oil (10cSt) two-dimensionally. Present study is the result of ?High speed three-dimensional direct measurement technology development for the evaluation of heat flux and flow of liquid metal? entrusted to the University of Tokyo by the Ministry of Education, Culture, Sports, Science and Technology of Japan(MEXT). [Preview Abstract] |
Monday, November 19, 2007 9:57AM - 10:10AM |
FI.00010: Transient temperature measurements of single water droplets over rough surfaces De Huang, Hui Hu, Chien-Pei Mao Advancing the technology for safe and efficient aircraft operation in atmospheric icing conditions requires a better understanding of the micro-physical phenomena associated with the accretion and growth of ice and the attendant aerodynamic effects. In order to elucidate the underlying physics associate with aircraft icing, experimental techniques capable of providing accurate measurements to quantify important ice growth physical processes such as dynamics of water droplets and transit heat transfer inside water droplets over rough surfaces are highly desirable. In the present study, we present the research progress made in our recent effort to develop and implement a novel molecular tagging thermometry (MTT) technique for the transient temperature measurements of water droplets over rough surfaces to quantify the unsteady heat transfer process inside convectively cooled/heated water droplets in order to improve our understanding about icing physics for various aircraft icing applications. [Preview Abstract] |
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