Application of multivariate outlier detection to fluid velocity measurements

Griffin, John; Schultz, Todd; Holman, R.J.; Ukeiley, Lawrence; Cattafesta, Louis N.

doi:10.1007/s00348-010-0875-3

Cited by 38 publications

(14 citation statements)

References 20 publications

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“…A multivariate outlier detection (MVOD) algorithm was applied to further improve the quality of the vector fields. The algorithm was developed by Hubert and Van der Veeken (2008), while Griffin et al (2010) successfully applied it to velocity field data in an analysis similar to the one performed here.…”

Section: Particle Image Velocimetrymentioning

confidence: 98%

Leading edge slot blowing on an open cavity in supersonic flow

2012

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Supersonic flow over an open cavity can create intense pressure loads on the surfaces within the cavity. In order to combat these loads, the development of a control scheme to reduce them is becoming increasingly important for many engineering applications. The present study implements steady leading edge blowing through various configurations of spanwise-aligned rectangular leading edge slots. The effects of this control on the flow field were examined to determine the suppression mechanisms exploited by the leading edge blowing. The cavity studied here had a length-to-depth ratio of 6 and was placed in a freestream flow with a Mach number of 1.4. Actuators with one continuous slot and three and five segmented slots spanning the width of the cavity were installed at the leading edge. Surface pressure reductions of nearly 45% were achieved on the aft wall of the cavity using the 5-slot configuration. Velocity field measurements acquired through 2-component (streamwise-aligned measurement plane) and 3-component stereoscopic (cross-stream-aligned measurement plane) particle image velocimetry revealed the presence of streamwise-aligned vortices created by the segmented slots. These act to significantly alter the shear layer formed at the mouth of the cavity creating highly three-dimensional flow field features.

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Section: Particle Image Velocimetrymentioning

confidence: 98%

Leading edge slot blowing on an open cavity in supersonic flow

2012

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“…To do so in a most adapted and efficient way, following e.g. [13], we choose to rely on temporal statistics computed by bin averaging, that will be introduced to compute mean flow fields (see section V D). As already noted in the PTV literature, such an approach, when available, is more efficient for turbulent flows than relying on comparisons to a spatial neighborhood.…”

Section: B Processing Parametersmentioning

confidence: 99%

“…As already noted in the PTV literature, such an approach, when available, is more efficient for turbulent flows than relying on comparisons to a spatial neighborhood. Contrary to [13] however, we here rely on a simpler combination of univariate statisti-cal rejection rules, as we choose to reject a given vector if any of its (u, v, w) components deviates from more than three standard deviations from its mean (the latter two referring to that of the bin to which the vector belongs).…”

Section: B Processing Parametersmentioning

confidence: 99%

Double-frame tomographic PTV at high seeding densities

et al. 2020

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A novel method performing 3D PTV from double frame multi-camera images is introduced. Particle velocities are estimated by following three steps. Firstly, separate particle reconstructions with a sparsity-based algorithm are performed on a fine grid. Secondly, they are expanded on a coarser grid on which 3D correlation is performed, yielding a predictor displacement field that allows to efficiently match particles at the two time instants. As these particles are still located on a voxel grid, the third, final step achieves particle position refinement to their actual subvoxel position by a global optimization process, also accounting for their intensities. As it strongly leverages on principles from tomographic reconstruction, the technique is termed Double-Frame Tomo-PTV (DF-TPTV). Synthetic tests on a complex turbulent flow show that the method achieves high particle and vector detection efficiency, up to seeding densities of around 0.08 particles per pixel (ppp), while its root-mean-square error of velocity estimation is lower to that of state-of-the-art similar methods. Results from an experimental campaign on a transitional round air jet at Reynolds number 4600 are also presented. During the tests, seeding density varies from 0.06 to 0.03 ppp on average. Associated to an outlier rejection scheme based on temporal statistics, DF-TPTV vector fields truthfully correspond to the instantaneous jet dynamics. Quantitative performance assessment is provided by introducing statistics performed by bin averaging, upon assuming statistical axisymmetry of the jet. Mean and fluctuating axial velocity components in the jet near-field are compared with reference results obtained from planar PIV at higher seeding density, with an interrogation window of size comparable to that of the bins. Results are found to be in excellent agreement with one another, confirming the high performance of DF-TPTV to yield reliable volumetric vector fields at seeding densities usually considered for tomographic PIV processing, or even higher.

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Section: Particle Image Velocimetrymentioning

confidence: 99%

On the Flow Physics of Effectively Controlled Open Cavity Flows

Ukeiley¹,

Cattafesta²

2013

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Standard Form 298 (Rev. 8/98) REPORT DOCUMENTATION PAGEPrescribed by ANSI Std. Z39.18 Form Approved OMB No. 0704-0188The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

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Application of multivariate outlier detection to fluid velocity measurements

Cited by 38 publications

References 20 publications

Leading edge slot blowing on an open cavity in supersonic flow

Leading edge slot blowing on an open cavity in supersonic flow

Double-frame tomographic PTV at high seeding densities

On the Flow Physics of Effectively Controlled Open Cavity Flows

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