气流作用下同轴带电射流的不稳定性研究

发布时间：2019-01-21 19:24

【摘要】：通过对气体驱动同轴电流动聚焦的实验模型进行简化,开展了电场力和惯性力共同作用下同轴带电射流的不稳定性理论研究.在流动为无黏、不可压缩、无旋的假设下,建立了三层流体带电射流物理模型并得到了扰动在时间域内发展演化的解析形式色散关系,利用正则模方法求解色散方程发现了流动的不稳定模态,进而分析了主要控制参数对不稳定模态的影响.结果表明,在参考状态下轴对称模态的最不稳定增长率最大,因此轴对称扰动控制整个流场.外层气流速度越高,气体惯性力越大,射流的界面越容易失稳.内外层液-液同轴射流之间的速度差越大,射流越不稳定.表面张力对射流不稳定性起到促进作用.轴向电场对射流不稳定性具有双重影响:当加载电场强度较小时,射流不稳定性被抑制;当施加电压大于某一临界值时,轴向电场会促进射流失稳.临界电压的大小与界面上自由电荷密度和射流表面扰动发展关系密切.这些结果与已有的实验现象吻合,能够对实验的过程控制提供理论指导.
[Abstract]:By simplifying the experimental model of gas-driven coaxial electric flow focusing, the instability theory of coaxial charged jet under the combined action of electric field force and inertial force is studied. Under the assumption that the flow is non-viscous, incompressible and non-rotating, the physical model of three-layer fluid charged jet is established, and the analytical formal dispersion relation of the evolution of disturbance in time domain is obtained. The unstable modes of the flow are found by using the regular mode method to solve the dispersion equation, and the influence of the main control parameters on the unstable modes is analyzed. The results show that the most unstable growth rate of axisymmetric mode is the largest under the reference state, so the axial symmetric disturbance controls the whole flow field. The higher the outer flow velocity, the greater the inertial force of the gas, and the easier the interface of the jet is to destabilize. The greater the velocity difference between the inner and outer layer liquid-liquid coaxial jet, the more unstable the jet. Surface tension promotes jet instability. The axial electric field has a double effect on the jet instability: the jet instability is suppressed when the electric field intensity is small, and when the applied voltage is greater than a certain critical value, the axial electric field will promote the jet instability. The critical voltage is closely related to the free charge density at the interface and the development of jet surface disturbance. These results are consistent with existing experimental phenomena and can provide theoretical guidance for experimental process control.
【作者单位】：中国科学技术大学近代力学系;
【基金】：国家自然科学基金(11472270,81327803,11621202) 中央高校基本科研业务费专项资金资助项目
【分类号】：O358

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