Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E14: Experimental Techniques III: Pressure Sensitive Paint |
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Chair: James Gregory, Ohio State University Room: 302 |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E14.00001: Identification of the resonant modes in supersonic impinging jets using fast response pressure sensitive paint Timothy Davis, Adam Edstrand, Farrukh Alvi, Louis Cattafesta, Daisuke Yorita, Keisuke Asai High speed impinging jets have been the focus of several studies owing to their practical application and resonance dominated flow-field. The current study utilizes fast-response pressure sensitive paint (PSP) to examine the jet instability modes of a Mach 1.5 normally impinging jet. These modes are associated with high amplitude, discrete peaks in the power spectra and can be identified as having either axisymmetric or azimuthal modes. Phase-averaged images are acquired at various nozzle to plate spacings and at frequencies of several kHz. Using an unsteady pressure transducer on the impingement surface as a reference signal, a high speed LED with a wavelength of 460 nm is used to illuminate the PSP. The paint fluorescence is then recorded with a CCD camera. The average pressure distribution is removed from the acquired images, resulting in the phase-averaged unsteady pressure distribution. The processed images reveal axisymmetric modes for all nozzle to plate spacings tested except at 4 jet diameters. At this spacing, three distinct resonant modes are identified. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E14.00002: Simultaneous pressure and velocity measurements using multi-dye microspheres implementing an intensity-ratio method Daniel Lacroix, Julian Massing, Christian Cierpka, Guo-Shi Li, Dana Dabiri, Gamal Khalil Luminescent pressure and temperature sensitive paints have been used to quantify pressure and temperature on surfaces, but not in flow fields. By incorporating pressure-sensitive, temperature-sensitive, and reference (non-sensitive) dyes into microspheres, which are then seeded into flow and imaged using high sensitivity EMCCDs, it will be possible to obtain pressure and temperature simultaneously. The pressure and temperature measurement methodologies are coupled with existing particle image velocimetry (PIV) methods to obtain simultaneous pressure, temperature, and velocity. Current research is focused on pressure and velocity measurements of these aerosolized microspheres using multiple cameras and calculating the ratio between the imaged pressure-sensitive and reference intensities. Detailed post-processing, which shows that the standard deviation of the ratios are reduced from approximately 10{\%} to 5-6{\%} will be discussed. In addition, we will discuss the implementation of the intensity-ratio method as well as the calibration process for determining pressure. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E14.00003: Pressure and velocity field measurements of pulsating flow in a square channel y-junction Markus Pastuhoff, Athanasia Kalpakli, P. Henrik Alfredsson The pressure and velocity fields in a y-junction of a square ($40\times 40$~mm$^2$) cross-section channel were investigated during pulsating flow. One of the sides of the channel was covered with fast responding pressure sensitive paint (PSP) whereas the velocity field at the channel center parallel to the PSP surface was measured using particle image velocimetry (PIV). The flow conditions, in terms of mass flow rate and pulsation frequency, were selected to resemble the flow inside an exhaust manifold of a small internal combustion engine, although the gas was at room temperature. The mass flow was varied between 10 and 130~g/s with pulsations between 0 and 80~Hz. For both the PSP and the PIV measurements images were acquired unsynchronized to the pulses using a high-speed camera and phase averages were formed {\it a posteriori}. The use of PSP together with PIV demonstrates how the two techniques can be used to verify and complement each other, PIV excelling at the lower mass flow rates and PSP at the higher. It is shown that the signal-to-noise ratio for PSP at low velocities can be enhanced using a technique based on singular value decomposition.\footnote{Pastuhoff, M., Yorita, D., Asai, K. \& Alfredsson, P.H. 2013 {\it Meas. Sci. Technol.} {\bf 24}, 075301.} [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E14.00004: Temperature Cancellation Method of Motion-Capturing Pressure-Sensitive Paint System Hirotaka Sakaue, Yuki Yamada, Taika Okabe, Takeshi Miyazaki Motion-capturing pressure-sensitive paint system uses two luminescent outputs to extract the pressure field on an aerodynamic object. This uses a luminescent imaging technique to relate the luminescent output to the pressure. In the previous study, this system is applied to capture the time-resolved unsteady pressure fields on a fluttering airfoil, and a bullet-shaped model. Pressure-sensitive paint (PSP) has a temperature dependency, which is a major error source for the PSP measurement. Motion-capturing PSP system also involves the temperature dependency of PSP itself. In the presentation, we propose a temperature-cancellation method of the motion-capturing PSP system. This method does not require a separate temperature measurement for the temperature correction that is advantage for capturing the pressure field on a moving object. [Preview Abstract] |
Sunday, November 24, 2013 5:37PM - 5:50PM |
E14.00005: Characterizations of Inorganic Electro-Luminescence as an Excitation Source of Pressure-Sensitive Paint Measurement System Yoshimi Iijima, Hirotaka Sakaue Electro-luminescence based pressure-sensitive paint (EL-PSP) system uses an inorganic EL as an excitation source for a PSP measurement. It can be directly applied onto a PSP model to eliminate a remote illumination, and gives a uniform illumination on a PSP model without moving/re-directing the illumination. The temperature dependency of the EL-PSP system can be reduced by the opposite temperature dependency of the EL and PSP. An inorganic EL needs an AC input for illumination that creates a periodic excitation of a PSP. It is necessary to characterize the periodic illumination of the EL in terms of a PSP excitation source. At present, it is found that a single pulse of the EL is dependent on the temperature but independent of the pressure. In the presentation, we discuss further the characterizations of the EL as an illumination source of PSP. These include the frequency of the EL illumination and the illumination pattern. [Preview Abstract] |
Sunday, November 24, 2013 5:50PM - 6:03PM |
E14.00006: Surface Pressure Measurements from Multiline Single-Component Molecular Tagging Velocimetry David A. Olson, Ahmed M. Naguib, Manoochehr M. Koochesfahani This study considers the feasibility of estimating the surface pressure distribution based on high-resolution single-component molecular tagging velocimetry. This approach would be helpful in situations where it is not practical to instrument a surface with pressure taps/sensors. The method relies on the connection between the surface pressure gradient and the second order wall-normal derivative of the velocity tangent to the wall. We show the application of this approach to measuring the surface pressure distribution on the circular cylinder in cross flow at Re = 6,000. Results compare favorably with data in the literature. [Preview Abstract] |
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