CMC非牛顿液滴撞击壁面铺展最大距离模型的研究

Study on the model of the maximum spreading diameter of CMC non-Newtonian droplets that impact on a solid surface

目的:由于非牛顿液滴在撞壁过程中粘度变化复杂,因此前人较少对非牛顿溶液撞壁进行研究。同时已有牛顿模型中关于粘性耗散项的定义较为简单,对最大扩散时间模型的研究也尚未达成共识。方法:利用高速摄像技术研究了3种不同质量浓度的羧甲基纤维素(CMC)非牛顿流体液滴撞击壁面的过程,使用Cross模型来表征CMC溶液的粘度,同时将流体粘度纳入粘性耗散项的计算中,利用毛细惯性时间来修正最大扩散时间模型。结果:基于能量守恒,推导出液滴撞壁铺展最大距离的模型,将模型与实验进行对比后发现数据误差在5%以内。结论:该模型能较好地预测本文实验以及文献中的数据,为涉及非牛顿液滴撞壁的实际应用提供了一定参考。

Aims:As the complexity of the viscosity change of non-Newtonian droplets during wall impact,there has been little investigation on the non-Newtonian solutions.In existing Newtonian models,the definition of the viscous dissipation term is rather easy;and there is no agreement on the maximum spreading time model.Methods:By using the high-speed camera,the process of non-Newtonian fluid droplets of three distinct concentrations of carboxymethyl cellulose(CMC)impacting the wall was investigated.The Cross model was used to characterize the rheological properties of the CMC shear-thinning solution.The characteristic velocity of the viscous dissipation term was modeled with the fluid viscosity;and the time to maximum spread could be expressed by the capillary-inertial time.Results:Based on energy conservation,a model for the maximum spreading diameter of droplets was deduced;and the model was found to be within 5%errors of experiments.Conclusions:The model successfully fits the experiment in this paper as well as the data in the literature.It provides a reference value for manufacturing activities that involve non-Newtonian droplet impact.