Multi-spatio-temporal scales PIV in a turbulent buoyant jet discharging in a linearly stratified environment

•Velocity fields are obtained for the first time experimentally for a buoyant jet propagating in a linearly stratified environment.•Using optimized instrumentation and optics, the temporal coverage spans 5 orders of magnitude.•The spatial dynamic range covers scales from 0.67 mm to 0.8 m, locally resolving the flow down to the Kolmogorov scale.•These performances can be obtained with relatively inexpensive machine vision cameras.•Turbulent kinetic energy spectra obtained from various PIV resolutions are compared and show its filtering effect. Time-resolved particle image velocimetry is implemented with a camera array and several laser sheets; this results in a multi-spatio-temporal scale system that is modular and flexible. The setup is optimized to capture global flow features, while locally resolving in space and time near the Kolmogorov scale. The apparatus relies extensively on machine vision CMOS cameras; they are inexpensive and stream to computer hard drive with virtually continuous time-resolved records (up to one hour for the current system). This leads to statistically converged data and also helps in minimizing down time between experimental runs. Details of the implementation and design of experiment are reported. The system instruments a vertical buoyant jet discharging in a linearly stratified environment. Refractive index matched aqueous solutions enable precise optical deployment. The density difference is 3% and the fluids have similar dynamic viscosity. The jet Reynolds number is 2.00×104 and is above the mixing transition. Such flows are typically challenging to instrument and few velocity field data are available to date. Velocity statistics are reported as well as first insights gained from the campaign.