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 A24: Experimental Methods IExperimental
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Chair: Nils Tilton, Colorado School of Mines Room: 703 |
Sunday, November 19, 2017 8:00AM - 8:13AM |
A24.00001: Multi-component velocity and temperature measurements in wall bounded turbulent flow utilizing a novel sensor. Clayton Byers, Marcus Hultmark A unique study of the simultaneous velocity and temperature field in a turbulent flow is performed. By utilizing the Nano-Scale Thermal Anemometry Probe (NSTAP) developed at Princeton in multi-mode operation, two components of velocity and temperature can be measured. This is achieved using a single sensing element by combining the methods of constant current hot-wire anemometry (CCA) and a new velocity measurement technique called elastic filament velocimetry (EFV). By switching between the two modes at high frequency, two orthogonal components of velocity as well as temperature can be obtained. The switched mode sensing system is deployed in a heated turbulent boundary layer to obtain the magnitude and direction (2D) of the velocity as well as the temperature. The sensor switching is characterized and shown to have a sufficiently high bandwidth to obtain unattenauted turbulence measurements. [Preview Abstract] |
Sunday, November 19, 2017 8:13AM - 8:26AM |
A24.00002: Uncertainty based pressure reconstruction from velocity measurement with generalized least squares Jiacheng Zhang, Carlo Scalo, Pavlos Vlachos A method using generalized least squares reconstruction of instantaneous pressure field from velocity measurement and velocity uncertainty is introduced and applied to both planar and volumetric flow data. Pressure gradients are computed on a staggered grid from flow acceleration. The variance-covariance matrix of the pressure gradients is evaluated from the velocity uncertainty by approximating the pressure gradient error to a linear combination of velocity errors. An overdetermined system of linear equations which relates the pressure and the computed pressure gradients is formulated and then solved using generalized least squares with the variance-covariance matrix of the pressure gradients. By comparing the reconstructed pressure field against other methods such as solving the pressure Poisson equation, the omni-directional integration, and the ordinary least squares reconstruction, generalized least squares method is found to be more robust to the noise in velocity measurement. The improvement on pressure result becomes more remarkable when the velocity measurement becomes less accurate and more heteroscedastic. The uncertainty of the reconstructed pressure field is also quantified and compared across the different methods. [Preview Abstract] |
Sunday, November 19, 2017 8:26AM - 8:39AM |
A24.00003: A finite element-based method for pressure estimation from measured velocity fields Kyle Sinding, Michael Krane The finite element method (FEM) is implemented to improve pressure estimation from experimental velocity data. This approach allows the flexibility of pressure boundary condition options of a pressure Poisson solver, while limiting the number of spatial derivatives of the measured velocity field necessary to specify the source term. A Taylor vortex is used as an analytical solution for the method of manufactured solutions to verify the proposed FEM. In addition, an assessment of error propagation to the estimated pressure field from the noisy measured velocity field is performed. This assessment is performed by adding noise to the Taylor vortex analytical velocity field to mimic measurement error. Finally, pressure estimates from the FEM-based approach are compared to estimates made by other approaches, from the same velocity data. While each method produces similar results the proposed FEM solution is the most consistent and requires the lowest spatial resolution. [Preview Abstract] |
Sunday, November 19, 2017 8:39AM - 8:52AM |
A24.00004: Unsteady pressures on a blunt trailing edge measured with an embedded pressure scanner Jonathan Naughton, Pourya Nikoueeyan, Michael Hind, John Strike, Matz Dahland, Steven Keeter Development of direct-mount pressure scanners can decrease the pneumatic tubing length required to connect the measurement ports to the scanner manifold resulting in improved dynamic range for unsteady pressure measurements. In this work, the performance of a direct-mount pressure scanner for time-resolved pressure measurement is demonstrated in a well-established flow; the pressure fluctuations near the base of flat plate is considered. The additive manufactured model is instrumented with a pressure scanner and flush-mounted high-speed pressure transducers. The configuration of the ports on the model allows for side-by-side comparison of the pressures measured via embedded pneumatic tubing routed to a pressure scanner with that measured by high-speed transducers. Prior to testing, the dynamic response of each embedded pressure port is dynamically calibrated via an in-situ calibration technique. Pressure data is then acquired for fixed angle-of-attack and different dynamic pitching conditions. The dynamic range of the measurements acquired via direct-mount scanner will be compared to those acquired by the high speed transducers for both static and dynamic pitching configurations. The uncertainties associated with Weiner deconvolution are also quantified for the measurements. [Preview Abstract] |
Sunday, November 19, 2017 8:52AM - 9:05AM |
A24.00005: Characterization of the embedded tubing response for flush-mounted pressure scanners Michael Hind, Pourya Nikoueeyan, John Strike, Jonathan Naughton, Matz Dahland, Steven Keeter In recent years, the demand for using pressure scanning modules for unsteady aerodynamic measurements has increased. The advent of additive manufacturing has enabled the design and utilization of pressure scanners mounted directly in the test model resulting in a reduction of the pneumatic tubing length. While this decreased tubing length can minimize the attenuation and latency that arise from friction in tubing, the pneumatic resonance can still distort the acquired pressure signal. Although previous work has shown the capabilities and limitations of Weiner deconvolution in reconstructing the surface pressure from the measured pressure at the end of a long tube, very little work has considered characterizing the short, complex geometry pneumatic tubing systems created with additive manufacturing. In this work, the dynamic response of different embedded pneumatic tubing configurations routed to a flush mounted pressure scanner are studied. The dependency of different distortions on the geometry of the embedded tubing system is studied, and the performance of Weiner deconvolution reconstruction is evaluated. Sources of random and bias error along with the uncertainty associated with the Weiner deconvolution are also considered and quantified. [Preview Abstract] |
Sunday, November 19, 2017 9:05AM - 9:18AM |
A24.00006: Evaluation of Low-Cost Multi-Hole Probes for Atmospheric Boundary Layer Investigation Solmoz Azartash-Namin, Jamey Jacob, Caleb Canter, Sean Bailey Low-cost multi-hole probes (MHPs) for atmospheric boundary layer (ABL) studies are investigated. Probes are designed using rapid prototyping methods through FDM, SLA, and other techniques for evaluation through calibration testing and comparison with probes manufactured through more traditional methods. Each probe is tested and validated to develop calibration curves and PIV is used to examine the flow field around the probe during both attached and separated conditions. Standard non-nulling calibration and data reduction methods were used showing performance characteristics of each probe. Impact of probe tip geometry and internal duct arrangements are examined. Multiple geometries, including hemispherical and pyramid, as well as multiple sizes are evaluated for both accuracy and sensitivity. Of the two primary geometric designs evaluated, the hemisphere 5HPs produced the most symmetric calibration curves with linearity between $\pm25^\circ$. Further issues related to optimized probe designs, manufacturing quality consistency, and sensor development are discussed. A custom weather data sensor package has been developed for flight testing in ABL studies and preliminary results are presented. Supported in part by National Science Foundation award numbers 1351411 and 1539070. [Preview Abstract] |
Sunday, November 19, 2017 9:18AM - 9:31AM |
A24.00007: Particle drag history in a subcritical post-shock flow -- data analysis method and uncertainty Liuyang Ding, Ankur Bordoloi, Ronald Adrian, Kathy Prestridge A novel data analysis method for measuring particle drag in an 8-pulse particle tracking velocimetry-accelerometry (PTVA) experiment is described. We represented the particle drag history, $C_{D}(t)$, using polynomials up to the third order. An analytical model for continuous particle position history was derived by integrating an equation relating $C_{D}(t) $with particle velocity and acceleration. The coefficients of $C_{D}(t)$ were then calculated by fitting the position history model to eight measured particle locations in the sense of least squares. A preliminary test with experimental data showed that the new method yielded physically more reasonable particle velocity and acceleration history compared to conventionally adopted polynomial fitting. To fully assess and optimize the performance of the new method, we performed a PTVA simulation by assuming a ground truth of particle motion based on an ensemble of experimental data. The results indicated a significant reduction in the RMS error of $C_{D}$. We also found that for particle locating noise between 0.1 and 3 pixels, a range encountered in our experiment, the lowest RMS error was achieved by using the quadratic $C_{D}(t)$ model. Furthermore, we will also discuss the optimization of the pulse timing configuration. [Preview Abstract] |
Sunday, November 19, 2017 9:31AM - 9:44AM |
A24.00008: Evaluation of the accuracy of the Rotating Parallel Ray Omnidirectional Integration for instantaneous pressure reconstruction from the measured pressure gradient Jose Moreto, Xiaofeng Liu The accuracy of the Rotating Parallel Ray omnidirectional integration for pressure reconstruction from the measured pressure gradient (Liu et al., AIAA paper 2016-1049) is evaluated against both the Circular Virtual Boundary omnidirectional integration (Liu and Katz, 2006 and 2013) and the conventional Poisson equation approach. Dirichlet condition at one boundary point and Neumann condition at all other boundary points are applied to the Poisson solver. A direct numerical simulation database of isotropic turbulence flow (JHTDB), with a homogeneously distributed random noise added to the entire field of DNS pressure gradient, is used to assess the performance of the methods. The random noise, generated by the Matlab function Rand, has a magnitude varying randomly within the range of $\pm $40{\%} of the maximum DNS pressure gradient. To account for the effect of the noise distribution pattern on the reconstructed pressure accuracy, a total of 1000 different noise distributions achieved by using different random number seeds are involved in the evaluation. Final results after averaging the 1000 realizations show that the error of the reconstructed pressure normalized by the DNS pressure variation range is 0.15$\pm $0.07 for the Poisson equation approach, 0.028$\pm $0.003 for the Circular Virtual Boundary method and 0.027$\pm $0.003 for the Rotating Parallel Ray method, indicating the robustness of the Rotating Parallel Ray method in pressure reconstruction. [Preview Abstract] |
Sunday, November 19, 2017 9:44AM - 9:57AM |
A24.00009: Fully developed pipe and triangular channel flow measurement using Magnetic Resonance Velocimetry Seungchan Baek, Wontae Hwang Magnetic resonance velocimetry (MRV) is a non-intrusive flow visualization method which is able to measure the 3 dimensional 3 component (3D3C) mean velocity field in complex geometries, using a healthcare MRI scanner. Since this technique is based on nuclear magnetic resonance (NMR), it is free from optical distortion and does not require tracer particles. Due to these powerful advantages, MRV usage is gradually expanding from biomedical fields to the engineering domain. In this study, we validate the performance of MRV by measuring fully developed pipe flow and compare measured data with time averaged DNS data. We then investigate the overall flow characteristics in a triangular channel with a sharp corner. At the sharp corner, boundary layer effects dominate and the effect of turbulence is reduced. This information has implications for engineering applications such as flow in a turbine blade internal cooling passage at the sharp trailing edge. [Preview Abstract] |
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