Experimental and numerical investigation of cross-sectional structures of liquid jets in supersonic crossflow

Abstract

The cross-sectional distributions of liquid jets in Mach 2.85 air crossflow were investigated experimentally and numerically. The Phase Doppler Anemometry system was adopted to obtain the droplet diameter and two velocity components. The experimental results show that the cross-sectional plane presents Omega shape. The Sauter Mean Diameter is 40 μm in the central region of the cross-sectional plane, and decreases from center to periphery. An increase in Sauter Mean Diameter is observed in the lateral boundary near the nozzle because of flow characteristics near the liquid column. The final Sauter Mean Diameter is 15 μm when the secondary atomization finished. The averaged traverse velocity peasants a stripe shape distribution and the high velocity value appears at the top and bottom region of the cross-sectional plane. Numerical results show three counter-rotating vortex pairs. The wall counter-rotating vortex pairs influence droplets motion and transport droplets. Smaller droplets with lower momentum flow into the vortex of the gas flow. Larger droplets with higher momentum flow along the wall toward lateral sides, resulting the spray foot structure of Omega shape. The nozzle diameter has effects on the cross-sectional distribution. With the nozzle diameter increasing, the cross-sectional plane becomes a Quasi-Omega shape but the non-dimensionalized height and width remain unchanged. A smaller nozzle diameter decreases the streamwise velocity near the wall and increases the negative traverse velocity, which leads to a larger spray foot.