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Proceedings Paper

Time-resolved laser Doppler and phase Doppler signal processing
Author(s): Peter Lehmann; Thomas Wriedt; Armin Schoene
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Paper Abstract

Signal processing in Laser Doppler Anemometry (LDA) and Phase Anemometry (PDA) is carried out in both, the time domain, for instance by counter processors, and the frequency domain by processors based on the Fast Fourier Transform (FFT). FFT based signal processing allows a frequency and phase determination even for rather low signal to noise ratios. Nevertheless, the time-varying amplitude, frequency, and phase difference of Doppler bursts contain relevant information which is generally not utilized by conventional signal analysis. By determining the bust envelopes of PDA bursts it is possible to improve the resolution of particle sizing which is restricted to a corresponding phase difference from 0 to 360 degrees when conventional FFT processing is used. Time-resolved phase difference and frequency determination allow an improved signal validation since effects like trajectory effects, particle coincidences within the measuring volume, droplet oscillations or non-spherical particle characteristics can be detected. In this contribution signal processing methods for determining such effects are introduced. Thee methods will offer improved signal processing facilities with respect to the above mentioned topics. Practical applications are demonstrated by simulation and experimental results.

Paper Details

Date Published: 29 September 1995
PDF: 12 pages
Proc. SPIE 2546, Optical Techniques in Fluid, Thermal, and Combustion Flow, (29 September 1995); doi: 10.1117/12.221529
Show Author Affiliations
Peter Lehmann, Univ. of Bremen (Germany)
Thomas Wriedt, Stiftung Institut fuer Werkstofftechnik (Germany)
Armin Schoene, Univ. of Bremen (Germany)

Published in SPIE Proceedings Vol. 2546:
Optical Techniques in Fluid, Thermal, and Combustion Flow
Soyoung Stephen Cha; James D. Trolinger, Editor(s)

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