A scheme for resampling, filtering, and subsampling unevenly spaced laser Doppler anemometer data

Pascale Biron, André G. Roy, James L. Best

Research output: Contribution to journalArticle

Abstract

Laser Doppler Anemometry (LDA) has proved a powerful tool for quantifying fluid turbulence and is increasingly being applied in fields such as fluvial sedimentology and geomorphology. When operated in the burst-signal processing mode, high-frequency velocity fluctuations are measured at irregular time internals. In many situations, there is a need to transform these data to obtain evenly spaced velocity values but at a lower frequency. However, clear guidelines for this type of data processing are lacking. Three steps are necessary in order to transform the original files into evenly spaced data: (1) resampling at the average sampling rate, (2) low-pass filtering with half-power frequency adjusted to the final sampling frequency, and (3) decimating at the desired frequency. The decision taken at each step will affect the resulting signal and may cause, if not assessed carefully, severe problems in the signal such as aliasing errors. This paper examines each stage of data processing and details the advantages and drawbacks of different techniques in relation to the effects on turbulence statistics (variance, instantaneous shear stress, etc.). A standard method and specific guidelines are finally proposed.

Original languageEnglish (US)
Pages (from-to)731-748
Number of pages18
JournalMathematical Geology
Volume27
Issue number6
DOIs
StatePublished - Aug 1 1995
Externally publishedYes

Keywords

  • aliasing
  • time-series analysis
  • turbulence statistics

ASJC Scopus subject areas

  • Mathematics (miscellaneous)
  • Earth and Planetary Sciences (miscellaneous)

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