【作者】 崔艳艳；

【导师】 沈胜强；

【作者基本信息】 大连理工大学 ， 热能工程， 2010， 硕士

【摘要】 带有自由表面的流动现象广泛存在于现实生活中,它与人类的生存和发展有着不可分割的联系。液滴与固体表面的撞击现象就是一种典型的自由表面流动问题。详细研究液滴撞击固体表面的动力学行为对研究这些自然现象和工业技术的发展起着至关重要的作用。本文根据流体力学控制方程建立了液滴撞击壁面的理论模型,利用流体动力学商业软件FLUENT的VOF二维模型,对液滴撞击倾斜壁面的动力学过程进行了重点考察,将模拟结果与实验数据进行比较分析,验证其正确性。通过改变相关参数,分析了液滴在壁面的流动状态,详细的研究了壁面特性、撞击速度、撞击角及液滴物性对变形过程的影响。本文最后提出了关于两相流计算的VOF三维模型,对液滴撞击水平及倾斜壁面的各个方向的变形情况进行了更深入的研究分析。结果表明；通过比较液滴撞击倾斜表面的模拟结果与实验数据,可以看出VOF数值模拟方法能够表现出液滴在撞击过程中的关键特征。当液滴撞击水平壁面时,液滴的流动是对称的,但是液滴撞击倾斜壁面时,液滴的流动是不对称的。对于液滴撞击水平表面,壁面湿润性的影响分别用静态接触角模型(SCA)和动态接触角模型(DCA)进行模拟,对比结果DCA模型更接近于实验观测值。对于液滴撞击倾斜壁面,壁面的可润湿性即壁面的接触角对液滴的流动状态有很大的影响。高润湿性表面仅仅表现出沉积铺展,低润湿性表面表现出明显的滑移现象；撞击速度越大,液滴铺展的长度越大；在相同的We数下,撞击角越小,液滴的铺展速度越快,最终铺展的程度越大；在相同的条件下,粘度大的液滴铺展速度慢,铺展的长度小。更多还原

【Abstract】 The free surface flow problems are commonly found out in the real life,it has inextricably linked with human survival and development. Droplets of liquid impact onto solid surfaces is a typical phenomenon of the free surface flow problem, The dynamic behaviors of droplet impact onto solid surface plays an important role in the study of nature phenomenon and the development of industrial technology.At first,this paper establishes the theoretical mode of the droplet deposition according fluid mechanical governing equation, VOF model in FLUENT of CFD software is applied to investigate the dynamic process of droplet impacting on inclined solid surface. In order to validated the model, simulated results are compared with experimental date. By altering concerned parameters, dynamics of droplet on solid surface are analyzed. Influence of parameters including feature of surface, impact velocity,impact angle and droplet properties on the deformation process is studied in detail. Next this article proposes three-dimensional VOF model based on 2D mathematical model, Then droplets impact onto horizontal and inclined surfaces were investigated by this model.The results has shown that despite of error in simulated results, by compared with experimental data, VOF method could capture the key feature of droplet dynamics when impacting the solid surface. In the case of normal impact.the flow is symmetric, but it is asymmetric for the oblique impact. During the process of droplets impact onto flat surfaces, The influence of surface wetting characteristics was investigated by using static contact angle (SCA) and dynamic contact angle (DCA) models. It was found that the DCA model is closer to the experiment observed value. During the process of droplets impact onto inclined surfaces, The flow state is seriously influenced by the wettability of surface, the high wettability surface sediment only shows spreading, the low wettability surface shows not only, spreading but also slip phenomenon; The impact velocity is bigger, the spreading diameter of droplet is bigger; In the same We,the impact angle is smaller, the spreading speed ids faster,and the last spreading relative diameter is bigger; The liquid characteristic such as viscosity has significant influence to the droplet impact dynamics. The smaller of the liquid viscosity, the bigger of the maximum relative diameter of the droplets can be obtained, and the spreading speed is slower.更多还原