Jet impingement using an adjustable spreading-angle sweeping jet

This experimental study proposes a master-slave fluidic oscillator that can produce sweeping impinging jets with adjustable spreading angles. The flow fields of the jet impingement on convex cylinders are measured using time-resolved particle image velocimetry (TR-PIV) in a water tank. By increasing the proportion of the flow rate that passes through the master layer from 0 to 1 (master flow rate, MFR), the range of the jet spreading angle can be smoothly increased from 0 degrees to about 100 degrees. This new design is then applied in impingement upon two convex cylinders with different diameters. The large cylinder has a diameter of D/D-h = 12.5, where D-h is the hydraulic diameter of the jet exit. When the jet spreading angle is maximized by setting MFR = 1, the jet can cover half of the large cylinder. On the other hand, for the small cylinder with a diameter of D/D-h = 2.5, the jet can enclose the whole convex surface when the jet spreading angle is minimized at MFR = 0. In addition, proper orthogonal decomposition (POD) analysis reveals different unsteady flow patterns induced by the jet interaction with the cylinders. This study demonstrates, very first time, flexibility of the novel sweeping jet oscillator and guides towards some potential applications. (C) 2020 Elsevier Masson SAS. All rights reserved.