540nm, pulsed laser design for particle image velocimetry applications

摘要

Different types of mechanical and digital devices for measuring the velocity of fluids such as rotameters, annubar tubes, orifice plates, are suitable options. A limitation of such devices is that the direct interaction with the flux causes unwanted perturbations affecting their results. In this work, the design of a 540nm pulsed fiber laser system for measuring the velocity of water as a fluid via the Particle Image Velocimetry (PIV) technique is proposed. In particle image velocimetry, the fluid motion is made visible by adding small tracer particles and from the position of these particles, at two instances of time, it is possible to determine the flow velocity. The proposed, made in-house, noncommercial PIV system consists of: a second harmonic generation Q-switched Yb-doped fiber laser emitting 540nm pulses, a CCD camera, a pair of cylindrical diverging lenses, reference beads, and the fluid under test. The Yb~(3+)-doped fiber laser itself is capable of producing 540nm, 5 - 15ns, 400mJ pulses at 500Hz - 15kHz repetition rates, suitable for PIV flow field studies. Full fiber laser design, in-house PIV system integration and flow field measurement results will be included in the presentation.