Denoising of time-resolved PIV for accurate measurement of turbulence spectra and reduced error in derivatives
Denoising of time-resolved PIV for accurate measurement of turbulence spectra and reduced error in derivatives
The accuracy of time-resolved PIV (TRPIV) turbulence measurements is limited by white noise, which reduces the signal-to-noise ratio (SNR) of small-scale velocity fluctuations. This paper demonstrates a novel energy filter that extends the concept of spectral noise subtraction to the time domain. The filter is equivalent to the spectral subtraction of white noise energy, and therefore it can recover the true signal energy. Its effectiveness is evaluated by comparing two-component (2C) TRPIV and constant temperature anemometry (CTA) measurements performed in grid-generated turbulence (Re ? = 90). The denoised PIV measurements exhibit a SNR equivalent to those of a high-performance CTA system. The temporal spectra of velocity fluctuations and derivatives are accurately recovered, with an improvement in dynamic range by a factor of \fancyscriptO(103) . The error in dissipation estimates derived from the frequency spectrum is reduced to approximately 2 %. The correlation coefficient between spatial gradients computed directly and those computed via Taylor’s hypothesis improves from 0.83 to 0.95. The mean-square error reduction is found to be equivalent in the frequency and wavenumber domains, although we observe that frequency domain filtering has a limited ability to improve the SNR of spatial spectra at high wavenumbers. The performance of the energy filter is shown to be sensitive to the convergence of the measured spectra; therefore, we provide sampling criteria to ensure optimal implementation in measurements of turbulent flows.
1561-1575
Oxlade, A. R.
7201c4ac-c8bf-45c2-b1bc-a1a6c6fdde53
Valente, P. C.
5344e1c8-2e62-4608-b331-0f31f0687df3
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Morrison, J. F.
63dd8544-13dc-4bae-9019-4956642cf3d2
November 2012
Oxlade, A. R.
7201c4ac-c8bf-45c2-b1bc-a1a6c6fdde53
Valente, P. C.
5344e1c8-2e62-4608-b331-0f31f0687df3
Ganapathisubramani, B.
5e69099f-2f39-4fdd-8a85-3ac906827052
Morrison, J. F.
63dd8544-13dc-4bae-9019-4956642cf3d2
Oxlade, A. R., Valente, P. C., Ganapathisubramani, B. and Morrison, J. F.
(2012)
Denoising of time-resolved PIV for accurate measurement of turbulence spectra and reduced error in derivatives.
Experiments in Fluids, 53 (5), .
(doi:10.1007/s00348-012-1375-4).
Abstract
The accuracy of time-resolved PIV (TRPIV) turbulence measurements is limited by white noise, which reduces the signal-to-noise ratio (SNR) of small-scale velocity fluctuations. This paper demonstrates a novel energy filter that extends the concept of spectral noise subtraction to the time domain. The filter is equivalent to the spectral subtraction of white noise energy, and therefore it can recover the true signal energy. Its effectiveness is evaluated by comparing two-component (2C) TRPIV and constant temperature anemometry (CTA) measurements performed in grid-generated turbulence (Re ? = 90). The denoised PIV measurements exhibit a SNR equivalent to those of a high-performance CTA system. The temporal spectra of velocity fluctuations and derivatives are accurately recovered, with an improvement in dynamic range by a factor of \fancyscriptO(103) . The error in dissipation estimates derived from the frequency spectrum is reduced to approximately 2 %. The correlation coefficient between spatial gradients computed directly and those computed via Taylor’s hypothesis improves from 0.83 to 0.95. The mean-square error reduction is found to be equivalent in the frequency and wavenumber domains, although we observe that frequency domain filtering has a limited ability to improve the SNR of spatial spectra at high wavenumbers. The performance of the energy filter is shown to be sensitive to the convergence of the measured spectra; therefore, we provide sampling criteria to ensure optimal implementation in measurements of turbulent flows.
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e-pub ahead of print date: 28 September 2012
Published date: November 2012
Organisations:
Aerodynamics & Flight Mechanics Group
Identifiers
Local EPrints ID: 354995
URI: http://eprints.soton.ac.uk/id/eprint/354995
ISSN: 0723-4864
PURE UUID: f781bab7-80b5-44bb-b721-c1802abc5b13
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Date deposited: 12 Aug 2013 10:15
Last modified: 15 Mar 2024 03:37
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Author:
A. R. Oxlade
Author:
P. C. Valente
Author:
J. F. Morrison
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