On the Lagrangian features of circular and semicircular jets via 3D Particle Tracking Velocimetry

Three-dimensional Particle Tracking Velocimetry was employed to characterize jets from circular and semi-circular pipes in the intermediate and far fields. Grid-interpolated velocity were used to validate the measurements, and confirmed the negligible effect of the pipe shape on the mean flow in the intermediate field. Several volumetric regions were defined to get Lagrangian statistical description of the flow from categorized particle trajectories. Probability density functions of the velocity fluctuations, particle acceleration, and curvature of the trajectories revealed common and distinctive features of the jets. The first one showed departure from the Gaussian distribution away from the core, and the acceleration exhibited heavy tails in the two jets; however the curvature pdf revealed distinctive footprint of the pipe shape.