Estimation of Power Spectra of Acoustic-Doppler Velocimetry Data Contaminated with Intermittent Spikes
Publication: Journal of Hydraulic Engineering
Volume 136, Issue 6
Abstract
Spectral analysis of velocity signals recorded by acoustic Doppler velocimetry (ADV) and contaminated with intermittent spikes remains a challenging task. In this paper, we propose a new method for reconstructing contaminated time series which integrates two previously developed techniques for detecting and replacing spurious spikes. The spikes are first detected using a modified version of the universal phase-space-thresholding technique and subsequently replaced by the last valid data points. The accuracy of the new approach is evaluated by applying it to identify and remove spikes and reconstruct the spectra of two clean data sets which are artificially contaminated with random spikes: (1) high-quality hot-wire measurement and (2) numerically simulated velocity time series with bimodal probability density distribution. The technique is also applied to reconstruct the spectra obtained from intentionally contaminated ADV measurements and compare them with ADV spectra at the same point in the flow obtained using proper ADV settings. Special emphasis is placed on testing the ability of the technique to reproduce realistic power spectra in flows with rich coherent dynamics. The results show that the power spectra of the reconstructed time series contain a filtered white noise caused by the steps in the reconstruction technique using the last valid data point. We show that even for a severely contaminated time series, the proposed method can accurately recover the power spectra up to the frequency corresponding to the half the mean sampling rate of the valid data points.
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Acknowledgments
This work was supported by the Minnesota Supercomputing Institute and NSF Grant Nos. NSFEAR-0120914 (as part of the National Center for Earth-Surface Dynamics) and NSFEAR-0738726. We acknowledge the assistance from Leonardo Chamorro and Joongcheol Paik who provided us the high-quality ADV, hot-wire, and numerical simulation time series, respectively. We are also grateful to Jeff Marr and Craig Hill for the complete set of ADV time series.
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Information & Authors
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Published In
Journal of Hydraulic Engineering
Volume 136 • Issue 6 • June 2010
Pages: 368 - 378
Copyright
© 2010 ASCE.
History
Received: May 7, 2008
Accepted: Jan 7, 2010
Published online: Jan 11, 2010
Published in print: Jun 2010
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