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A Model-Based Approach for Dual-Burst Processing of Laser Profile Velocimetry Signals

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3 Author(s)
Neumann, M. ; Lab. for Meas. & Testing Tech., Tech. Univ. Dresden, Dresden, Germany ; Fischer, A. ; Czarske, J.

In order to characterize turbulent flows, correlation measurements are a common procedure. Laser Doppler sensors are often applied for this task, but in the case of high seeding concentrations, the so-called dual-burst signals occur. These are caused by multiple particles passing the measurement volume at the same time. In this paper, a model-based signal processing approach is presented which is able to evaluate such distorted signals. In order to assess the performance of dual-burst algorithms, the Cramér-Rao lower bound is calculated for the first time. A comparison of this new technique with conventional dual-burst algorithms reveals a systematic error which is at least seven times lower and even makes an evaluation of the complete signal in some cases possible in the first place. As a result, the total frequency estimation uncertainty of dual-burst signals, which is directly linked to the velocity uncertainty, is improved by a factor of five and more. Hence, this new technique enables the precise evaluation of correlation functions and instantaneous velocity gradients of complex flows.

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Instrumentation and Measurement, IEEE Transactions on  (Volume:62 ,  Issue: 1 )