Based on Karman vortex street principle, central-body nozzle is expected to arouse cavitation in the discharged jet and then result in strong impact on acted object. To discover the influence of central-body on flow characteristics, under the same jet pressure of 15MPa, comparison between the two free water jet fields produced respectively by a central-body nozzle and a round nozzle was conducted. Phase Doppler particle anemometry (PDPA) was applied to measure velocity distribution, turbulent fluctuation and droplet diameter distribution at different traverse sections. Experimental results show that although the annular jet tends to concentrate soon after the central body, the radial diffusion of the jet discharged from the central-body nozzle is more obvious. For the two jets kinetic energy is well remained along the jet direction and high-velocity zone is wider near the jet axis of the central-body nozzle. For the jet discharged from the central-body nozzle, turbulent fluctuation near the jet axis is relatively weak. As for possible cavitation, the position is right after the central body and the reachable distance of cavitation effect is short, which produces an inevitable restriction on the nozzle’s application. And similar Sauter mean diameter (SMD) distribution profiles are found in the two jet fields especially when distance between nozzle and traverse section gets large. The study here provides quantitative and comparative information for the two nozzles and can be referred to in further study and optimal design of central-body nozzle.

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