Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session M24: Experimental Methods IVExperimental
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Chair: Brian Thurow, Auburn University Room: 703 |
Tuesday, November 21, 2017 8:00AM - 8:13AM |
M24.00001: Development of single shot 1D-Raman scattering measurements for flames Amelia Biase, Mruthunjaya Uddi The majority of energy consumption in the US comes from burning fossil fuels which increases the concentration of carbon dioxide in the atmosphere. The increasing concentration of carbon dioxide in the atmosphere has negative impacts on the environment. One solution to this problem is to study the oxy-combustion process. A pure oxygen stream is used instead of air for combustion. Products contain only carbon dioxide and water. It is easy to separate water from carbon dioxide by condensation and the carbon dioxide can be captured easily. Lower gas volume allows for easier removal of pollutants from the flue gas. The design of a system that studies the oxy-combustion process using advanced laser diagnostic techniques and Raman scattering measurements is presented. The experiments focus on spontaneous Raman scattering. This is one of the few techniques that can provide quantitative measurements of the concentration and temperature of different chemical species in a turbulent flow. The experimental design and process of validating the design to ensure the data is accurate is described. The Raman data collected form an experimental data base that is used for the validation of spontaneous Raman scattering in high pressure environments for the oxy-combustion process. [Preview Abstract] |
Tuesday, November 21, 2017 8:13AM - 8:26AM |
M24.00002: Combined PSP and PEC Testing Jack Kawell This research presents a technique that combines a pressure sensitive paint (PSP) with a photoelastic coating (PEC) to measure both pressure and strain simultaneously. Though this can be accomplished with high accuracy using measuring devices such as strain gauges and surface pressure ports, these point-wise methods do not have high spatial resolution, which is often required in aerodynamic testing. The use of PSP and PEC for measuring pressure and strain is well documented, but thus far, these techniques have been used separately. In this research, we layered a PSP over a PEC and conducted tests to verify the viability of this method for measuring pressure and strain simultaneously. We constructed a benchtop pressure chamber with a cantilever beam to control both the pressure and strain on a specimen. Then we verified and calibrated the new technique by altering the pressure and strain. Results will focus on the sensitivity of the technique and the decoupling of pressure and strain. In the future, this technique could be highly useful for aerospace applications or any other field where high-definition, unsteady pressure and strain fields across a surface are desired. [Preview Abstract] |
Tuesday, November 21, 2017 8:26AM - 8:39AM |
M24.00003: Experimental Investigations of Compressible Turbulent Boundary Layers with the Use of Nano-Scale Thermal Anemometry Probes (NSTAP) Katherine Kokmanian, Subrahmanyam Duvvuri, Sven Scharnowski, Matthew Bross, Christian J. Kaehler, Marcus Hultmark Nano-Scale Thermal Anemometry Probes (NSTAP) have been designed, tested and used in a wide variety of incompressible flows. These sensors are capable of measuring streamwise velocity fluctuations with an order of magnitude better resolution, both temporal and spatial, compared to conventional hot-wires, due to their miniature size and minute thermal mass (the heating element is only 60 microns long, 2 microns wide and 100 nm thick). Here we report recent efforts to redesign the NSTAP to withstand supersonic flow conditions. Work has been performed in Princeton's micro-nano fabrication laboratory in order to modify both the 2D layout and the 3D shapes of these sensors. The supersonic version of the NSTAP is evaluated in collaboration with Bundeswehr University. The ultimate objective of this work is to measure both fluctuating mass flow rate and total temperature in compressible turbulent boundary layers, by combining two supersonic sensors which operate at different overheat ratios. [Preview Abstract] |
Tuesday, November 21, 2017 8:39AM - 8:52AM |
M24.00004: Correlation Reconstruction Tomographic PIV Roderick La Foy, Pavlos Vlachos A new volumetric Particle Image Velocimetry technique was developed that outputs accurate velocity measurements up to very high seeding densities while requiring lower computational expenditure. This technique combines the tomographic and cross-correlation steps by directly reconstructing the 3D cross-correlation volumes. Since many particles contribute to a single correlation peak, this decreases the noise contributions from ghost reconstructions, allowing accurate velocity measurements to be made at exceptionally high seeding densities. Additionally the overall computational cost is lowered by combining the reconstruction and cross-correlation steps. Results comparing the errors of the new technique applied to both simulated and experimental data will be presented. [Preview Abstract] |
Tuesday, November 21, 2017 8:52AM - 9:05AM |
M24.00005: High-resolution velocity measurements using dual-view tomographic digital holographic microscopy Jian Gao, Karuna Agarwal, Joseph Katz A recently developed two-view tomographic digital holographic microscopy (DHM) system is used for measuring the flow around a pair of cubes with height of 90 wall units immersed in the inner layer of a turbulent channel flow at \textit{Re}$_{\mathrm{\tau }}=$2500. Matching of the two views at $\sim $1-$\mu $m precision is achieved by implementing a self-calibration procedure that determines the three-dimensional, three-component (3D3C) distortion function, which corrects the geometric mapping. The procedure has been tested using distorted synthetic particle fields, and then implemented on experimental data. The two views are used to overcome the reduced accuracy of DHM in the axial direction of the reference beam due to elongation of the reconstructed traces. Multiplying the two precisely-matched 3D intensity fields is used for truncating the elongated traces. The velocity distributions are obtained by 3D particle tracking guided by 3D cross-correlation of the truncated intensity fields along with other size/shape/smoothness constraints. As demonstrated by how divergence-free the data is, the resulting 3D3C velocity field is substantially more accurate than results obtained from single-view DHM. Results show that the cube is surrounded by a vorticity ``canopy'' that extends from upstream of its front surface to the separated region in its near wake. Nearly axial necklace vortices remain confined to the near wall region between the cubes, but expand rapidly behind them. [Preview Abstract] |
Tuesday, November 21, 2017 9:05AM - 9:18AM |
M24.00006: Vorticity field measurement using digital inline holography Kevin Mallery, Jiarong Hong We demonstrate the direct measurement of a 3D vorticity field using digital inline holographic microscopy. Microfiber tracer particles are illuminated with a 532 nm continuous diode laser and imaged using a single CCD camera. The recorded holographic images are processed using a GPU-accelerated inverse problem approach to reconstruct the 3D structure of each microfiber in the imaged volume. The translation and rotation of each microfiber are measured using a time-resolved image sequence -- yielding velocity and vorticity point measurements. The accuracy and limitations of this method are investigated using synthetic holograms. Measurements of solid body rotational flow are used to validate the accuracy of the technique under known flow conditions. The technique is further applied to a practical turbulent flow case for investigating its 3D velocity field and vorticity distribution. [Preview Abstract] |
Tuesday, November 21, 2017 9:18AM - 9:31AM |
M24.00007: Flow Analysis of a Rising Crude Oil Micro-Droplet Affected by Attached Microbial Streamers Matthew Amaro, Andrew White, Maryam Jalali, Jian Sheng Microfluidic experiments show bacteria flowing past a pinned crude oil droplet produce microbial aggregates and streamers on the oil-water interface. High speed DIC microscopy at 1000 fps for 1 sec with a sampling interval of 10 min captures the evolving flow and bacterial motility as well as adhesion, aggregation and streamer events. With bacteria as tracers, velocity measurements are acquired with in-house PIV-assisted PTV software. Flow fields with spatial resolution 2.5 $\mu$m are measured around an O(100) $\mu$m drop in a 700$\times$700 $\mu$m window. Full budgets of the 2D Navier-Stokes equation are faithfully resolved to determine pressure gradients by performing the balance over a control volume enclosing the droplet. Pressure gradients are integrated over the border of the control region to obtain pressure profiles at the leading and trailing edges. A momentum balance can be used to determine the drag induced by the drop and any attached streamers. Cases with and without streamers and their differing flow features are presented. Additionally streamers produce nonzero curl in the pressure gradient field providing a tool for identifying the position of otherwise invisible streamers. Ongoing experiments and future applications of the tools presented here will be discussed. [Preview Abstract] |
Tuesday, November 21, 2017 9:31AM - 9:44AM |
M24.00008: A novel approach for quantifying the zero-plane displacement of rough-wall boundary layers Manuel Ferreira, Eduardo Rodriguez-Lopez, Bharath Ganapathisubramani Indirect methods of wall shear stress (WSS) estimation are frequently used to characterise rough wall boundary-layer flows. The zero-plane displacement, hypothesised to be the vertical location where it acts, is often treated as a fitting parameter. However, it would be preferrable to measure both these quantities directly, especially for surfaces with large roughness elements where established scaling and similarity laws may not hold. In this talk we present a novel floating element balance that is able to measure not only the WSS but also the wall normal location at which it acts. While allowing compensation for mild static pressure gradients by means of a first-order analytical model. Its architecture is based on a parallel-shift linkage and it's fitted with custom built force transducers and a data acquisition system especially designed to achieve high Signal-to-Noise Ratios (SNR). The smooth-wall boundary-layer flow is used as benchmark to assess the accuracy of this balance. The values of skin friction coefficient show an agreement with hot-wire anemometry to within $2\%$ at a local Reynolds number $Re_{\theta} = 4\times10^3$ up to $10^4$. A rough surface of regularly distributed large elements is used to investigate the ability to infer the zero-plane displacement. [Preview Abstract] |
Tuesday, November 21, 2017 9:44AM - 9:57AM |
M24.00009: ABSTRACT WITHDRAWN |
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