荷电黏性液体射流线性不稳定性分析

Linear stability analysis for charged viscid liquid jets

根据线性不稳定性理论分析了扰动压强场和扰动电场,对荷电液体射流受力特性进行分析,建立了荷电黏性液体射流色散方程,通过数值计算分析了射流速度、荷电电压及黏度对荷电液体射流不稳定性的影响.研究结果表明:增加射流速度或荷电电压均能使射流不稳定性增加,表面波最大增长率及其对应的最优波数、最大波数均增大,射流破碎形成的液滴特征尺寸减小.黏度的提高使射流趋于稳定不易破碎,表面波最大增长率及其对应的最优波数减小,射流破碎形成的液滴特征尺寸增大,而最大波数保持不变.射流速度在0～1 m/s范围内,非荷电与荷电情况下0阶表面波始终存在;非荷电时,只有当射流速度达到一定数值时1阶表面波才出现,荷电后,1阶表面波在更小的射流速度时即可出现;0阶表面波最大增长率大于1阶表面波最大增长率,在液体射流破碎过程中占据主导地位.

Based on the linear instability theory, the perturbed pressure and electric fields were analyzed and the dispersion equation of charged viscid liquid jet was established by force characteristics analysis. Through numerical computations, the influence of jet velocity, charged voltage and viscosity on the instability of charged jet were obtained. The results show that with increasing jet velocity and charged voltage, the maximum of wave growth rate, corresponding optimal wave number, and the maximum of wave number get larger, and the droplet size gets smaller. Viscosity always makes the jet more stable. When viscosity is higher, the maximum of wave growth rate and corresponding optimal wave number get smaller so that the droplet size is bigger, but the maximum of wave number remains unchanged. For the jet with a velocity in the range of 0 to 1 m/s, the O-order wave always exists re- gardless whether the jet is charged or not. The 1-order wave appears on the surface of uncharged liquid jet only when the jet velocity reaches a certain value and high voltage makes the 1-order wave occur in a lower jet velocity. The 0-order wave is dominant in jet breakup because the maximum growth rate of 0-order wave is larger than that of 1-order wave.