电场作用下无黏聚焦射流的时间不稳定性研究

基于电场作用下的流动聚焦实验建立了简化的理论模型,开展了带电同轴液气射流的时间不稳定性分析.在无黏假设下,得到了扰动在时间域内发展演化的解析形式的色散关系,分析了主要控制参数对不稳定模态的影响.结果表明,只有轴对称扰动和第一类非轴对称扰动在时间域内是增长的;液气界面的表面张力对轴对称扰动有着双重影响而对非轴对称扰动起抑制作用;外层气体的流速以及密度的增加均能促进射流的失稳.这些结论与实验结果是定性一致的.结果也表明,在不考虑初始界面电荷密度时,单一的轴向电场能抑制射流的失稳. 

TEMPORAL INSTABILITY STUDY OF INVISCID FOCUSED JETS UNDER AN ELECTRIC FIELD

A temporal instability analysis of an electrified coaxial liquid-gas jet was performed based on the simplified theoretical model of the flow focusing under an electric field.On the assumption that the fluids are inviscid,an analytical dispersion relation of disturbances growing in the temporal regime was obtained and the effects of main controllable parameters on the unstable modes were analyzed.The results indicate that,only the axisymmetric and the first non-axisymmetric disturbances grow in the temporal regime;the surface tension has two-fold influences on the axisymmetric instabilities and suppresses the non-axisymmetric instabilities;the increases of velocity and density of the external gas streams can definitely promote the jet instabilities.These conclusions are consistent with the experimental results qualitatively.The results also show that the single axial electric field can suppress the jet instability when the initial electric charge density on the jet surface is neglected.On the whole,the theoretical investigation will be helpful for understanding the physical mechanisms of the flow focusing under an electric field and for providing guidance to practical applications.