Aerial Shape Analysis of Millimeter-scale Low-speed Free Jets in Circular Tubes
Free jet is a common phenomenon in various types of mechanical equipment and pipeline facilities.The study on the air morphology of low-speed jet in millimeter round pipe can provide a basis for the analysis of jet distance,water inflow attitude,energy dissipation and noise.In this study,the aerial shape of low-speed jets in circular tubes with millimeter-level diameters was investigated.The effects of different low speeds and tube diameters on jet continuity and breakup were examined using 4,5,and 6 mm round tube jets.A high-speed camera was utilized to capture changes in the jet breakup point and broken water droplets.The analysis included measuring and analyzing the flow velocity,continuous length,and broken water droplet diameter,as well as their relationship with the Reynolds number(Re)and the Weber number(We).The findings indicate that,when the pipe diameter is constant,the continuous length of the jet increases with the outlet flow rate.However,as the pipe diameter increases,the increase in the continuous length becomes smaller.Additionally,when the flow rate remains the same,the continuous length decreases as the inner diameter of the nozzle increases.Moreover,the continuous length of the jet decreases with increasing Re and We numbers.Notably,when We is in the range of 3 000 to 3 500,the relationship changes from a curve to a straight line.The polymerization process of broken water droplets is described in detail.A fitting relationship between the continuous length of the jet and We is provided.Furthermore,the study analyzed the size,aggregation method,and vibration characteristics of the broken main water droplets and satellite water droplets.A linear relationship exists between the size of water droplets and the inner diameter of the nozzle,both of which increase proportionally with an increase in the inner diameter of the nozzle.The size of the satellite water droplets is approximately in line with the size anticipated by Rayleigh's linear instability theory.Various polymerization methods result in different levels of air mixing,offering insights into water inflow posture,energy dissipation,and noise reduction under varying conditions.The vibration period of the water droplets was determined to be 25.67 ms.
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