Water jet velocity uncertainty in laser Doppler velocimetry measurements

The present work deals with the uncertainty evaluation in water jet velocity measurements carried out by means of a laser Doppler dual-incident-beam velocimeter in reference-beam configuration developed at the WJLab (Water Jet Laboratory of Dipartimento di Meccanica of Politecnico di Milano). The applied experimental procedure makes it possible to calculate the measurement uncertainty through the determination of its various components. Once uncertainty is known, the laser Doppler system is suitable for objective and significant velocity evaluations but also for improvements allowed by the knowledge of the most effective uncertainty sources. Such a subject is typically not considered by the specific water jet literature, but is becoming more and more important due to the evolution of water jet machining towards high precision applications.

► Method for determining the uncertainty sources in laser Doppler water jet velocity measurements. ► Characterisation of a reference-beam laser Doppler dual-incident-beam velocimeter. ► Validation of the LDV system design, based on two separate modules. ► Negligible role of scattered light frequency uncertainty in laser Doppler velocimetry. ► Main uncertainty sources estimation: CCD sensor resolution, fringes image analysis algorithm.