Experimental study of a jet in a crossflow at very low Reynolds number

Abstract

Flow visualizations and phase-averaged particle image velocimetry (PIV) measurements of a jet in crossflow configuration at very low Reynolds numbers (Rej ≃ 100) are performed in a water tunnel for jet-to-cross-stream velocity ratios R ranging from 1.5 to 4.5. The PIV vector fields and flow visualizations, carried out by injecting methylene blue dye and by the laser induced fluorescence (LIF) technique, are analysed to characterize the effect of R on the formation and evolution of large-scale vortices. It is shown that two distinct flow regimes are established depending on R, with R ≃ 3 being a transitional value. At low R, the longitudinal vorticity dynamics is dominated by the so-called wake-like structures which are shown to be strictly connected to the streamwise counter-rotating vortices (CRVP) which drive the destabilization of the jet flow. On the other hand, at large R, vortices with positive and negative vorticity are coupled together. The establishment of these different behaviours is interpreted physically as an effect of the jet Reynolds number which plays an essential role on the destabilization mechanisms which lead to the formation of the jet shear-layer structures. In any case, the onset of instability is driven by mechanisms which are different from those characteristic of free jets.

Flow Characteristics of a Low Reynolds Number Jet in Crossflow with an Obstacle Block

“…In the presented cases, the corresponding A and n are listed in Table 1. The studied cases in this paper have shown a good agreement with the experimental results (Camussi 2002) within 5% error. This demonstrates that the large eddy simulation has higher accuracy in the studied cases.…”

“…The formations of three special shocks including a barrel shock, a bow shock, and a separation-induced shock wave were observed. Camussi [9] performed the flow visualizations and phase-averaged particle image velocimetry (PIV) measurements of a jet in crossflow configuration at very low Reynolds numbers (Re=100), which were achieved in a water tunnel with the velocity ratios ranging from 1.5 to 4.5. The corresponding results showed that the principal vortex systems from the interaction of the jet with the crossflow at low Reynolds number were the same as those observed at larger Reynolds numbers.…”

2D PIV measurement on the interaction zone between two parallel planar jets in a crossflow

“…Experimental studies on the circular jet to date 16,25,26 found from instantaneous results that, when the jet is ejected into a crossflow ambient, horseshoe vortices (HSV) can develop in the leading side of the jet orifice and roll up. Then it will wrap around the jet orifice, evolve to the downstream field, and become coherent vortices.…”

“…[34][35][36] As previously mentioned in Section I, those large-scale vortices include, in reference to a circular jet, CRVP, HSV, WV, UV, and RLV. 16 Due to the approximately 2-D character, the main flow feature of a planar jet is the RLV. However, since the shape does not resemble a ring, it is termed as a Shear Layer Vortices (SLV) in the planar jet.…”

Point and planar LIF for velocity-concentration correlations in a jet in cross flow

“…While there has been many investigations of jets in a free cross flow, only few measurements have been presented for jets in a narrow duct, e.g. see Cenedese and Angelis (1998) and Camussi et al (1998). The present study considers a single jet entering fully developed laminar and turbulent flow in a straight duct with a square cross section.…”