Abstract
In order to study the spatial breakup characteristics of the initial section of low-pressure jets, an experiment was performed to investigate the flow fields and concentration fields of jet flows with different nozzle geometric parameters and also the different working pressures using a particle image velocimetry system. The flow field of different axial planes, axial time-average velocity, and the length of the initial sections of jet flows were also analyzed. A numerical simulation was carried out using finite volume method and volume of fluid–level set method to describe the breaking process of the initial section, capturing unstable development of gas–fluid interface, measuring the length of the initial sections of jet flows. Both experiment and simulation results show that the broken degree of jet is more intense for nozzles with smaller aspect ratio; the outlet velocity of jet increases with the working pressure; and the value of [Formula: see text] decreases with the increase in pressures in the same cross section of jet flow. The experimental values are slightly higher than the simulation values with an error of <8% for the cross-sectional velocity distribution. The initial length of jet increases with pressures, where the experimental values are lower than the simulation values with an error of <5%. The experimental data from particle image velocimetry agreed well with the simulation results. Therefore, the accuracy and reliability of the particle image velocimetry experiment and the computational fluid dynamics result simulation were both validated.
Highlights
The free surface flow of low-pressure jet and gas–liquid interface flow has attracted many researches in agricultural sprinkling irrigation for the purpose of uniform spraying
This article presents the advanced applications of particle image velocimetry (PIV) technique and numerical simulation method to measure the flow field of different axial planes, axial timeaverage velocity, and the length of the initial sections of jet flows emitted by the sprinkler with different nozzle geometric parameters and working pressures
From the results of this study, the following conclusions can be drawn: 1. In the experimental conditions, for the same type nozzle, the outlet velocity of jet flow increases with an increase in pressure which resulted in the initial length of jet becoming longer
Summary
The free surface flow of low-pressure jet and gas–liquid interface flow has attracted many researches in agricultural sprinkling irrigation for the purpose of uniform spraying. Noninvasive measuring techniques have been proposed to describe the flow properties through computational visualization methodologies such as particle image velocimetry (PIV), particle tracking velocimetry (PTV), and phase Doppler particle anemometry (PDPA) for two-dimensional flow analysis. Those techniques were mainly used for the measuring of atomization jets, in which the nozzle has a small bore or working under the high pressure and temperature. PDPA was applied to measure nonintrusively typical parameters such as average velocity, root mean square (RMS) velocity, and droplet diameter of a fan water jet flow.[14]
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