要开展凝胶推进剂液滴燃烧特性的实验研究,必须首先形成凝胶推进剂液滴,在毛细管末端形成液滴是常用的液滴生成方法之一.为了揭示毛细管末端凝胶推进剂液滴的形成过程,求解了轴对称坐标系下的N-S方程,采用VOF(volume of fluid)方法捕捉液滴形成过程中气液交界面的演化规律,研究了无量纲液滴颈部直径DN/D0和无量纲液滴高度L/D0随时间的变化规律,并且与实验结果进行比较,验证了数值模型的可靠性.计算结果表明:在液滴形成过程中,液滴不是一直处于稳态；液滴颈部存在较大的剪切率,导致粘度下降,进而加快了颈部的断裂和自由液滴的形成；颈部断裂后,与液滴相连的部分迅速与液滴融合,出现很大的正向速度,而与毛细管末端相连的部分迅速收回,出现很大的负向速度.%Understanding drop formation of gel fuel is the First stage to conduct experimental investigation on combustion characteristics of single gel fuel droplet, and the formation of liquid drops at the end of a capillary tube is one of conventional methods. In order to investigate the formation of gel propellant drops at the end of a capillary tube, the Navier-Stokes equations were solved, and the VOF ( volume of fluid) method is employed to track the gas/liquid interface during process of drop formation. The variation of dimensionless neck diameter DN/DO and dimensionless drop height L/DO with time was analyzed, which agreed with the existing experimental results and validated the numerical model. The results show that drop is not always at the steady state; there is high shear rate at the drop neck, leading to dynamic viscosity decreasing and drop pinch-off; then drop pinch-off, the part of conjoint drop, coalesces into drop rapidly, and high positive velocity appears; however, the part of conjoint capillary tube coalesces into gel propellant at the end of capillary tube rapidly, and the high negative velocity appears.
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