Impact of mismatched and misaligned laser light sheet profiles on PIV performance

Interactions between a shock and turbulent features in a Mach 2 compressible boundary layer

“…Furthermore, unlike the mean velocity, the measured turbulent stress profiles are dependent on the spatial resolution of the sensor utilised (Ligrani & Bradshaw 1987;Lee et al 2016). The integration window used for PIV evaluation has dimensions of 130 viscous units × 130 viscous units, while the laser sheet thickness is estimated to be approximately 0.5-1 mm (Grayson et al 2018), which corresponds to 150-300 viscous units. In contrast, the incompressible dataset is obtained utilising a cross-wire with dimensions of 13 viscous units × 13 viscous units, with a wire spacing of 7 viscous units.…”

The effect of spanwise wavelength of surface heterogeneity on turbulent secondary flows

“…The measurement plane is illuminated by a laser sheet generated from an InnoLas SpitLight Compact PIV 400 dual pulse Nd:YAG laser and a typical optical configuration. The thickness of the laser sheet is estimated using a method described in Grayson et al (2018), corresponding to x + ≈ 165 for the reference case SW-2. The flow is seeded with polyamide particles of 1-2 µm diameter.…”

Beam stability and warm-up effects of Nd:YAG lasers used in particle image velocimetry

“…In this study, a modular and flexible profiling system is used, consisting of a consumer digital camera and off-the-shelf components. Further details regarding this camera system can be found in Grayson et al [1].…”

“…The duration of these warm-up transients and their impact on laser behaviour is often underappreciated. Laser-based flow visualisation techniques, such as particle image velocimetry (PIV), are particularly sensitive to these changes in the performance of the laser system [1]. In practice, the magnitude of these warm-up behaviours is sufficient to interfere not only with experimental measurements, but also frustrate beam and optical alignment during the setup of an experiment.…”