Crown evolution kinematics of a camellia oil droplet impacting on a liquid layer

The phenomenon of droplet impact on an immiscible liquid is encountered in a variety of scenarios in nature and industrial production. Despite exhaustive research, it is not fully clear how the immiscibility of the liquid on which a droplet impacts affects the crown evolution. The present work experimentally investigates the evolution kinematics of a crown formed by the normal impact of a camellia oil droplet on an immiscible water layer. Based on discussion of dynamic impact behaviors for three critical Weber numbers (We), the radius of the crown and its average spreading velocity are compared with those of previous theoretical models to discuss their applicability to the immiscible liquid. The evolution kinematics (morphology and velocity) are analyzed by considering the effects of the We and layer thickness. Furthermore, the ability of crown expansion in radial and vertical directions is characterized by a velocity ratio. The results show that our experimental crown radius still follows a square-root function of evolution time, which agrees with the theoretical predictions. The dimensionless average spreading velocity decreases with We and follows a multivariate power law, while the dimensionless average rising velocity remains constant. The velocity ratio is shown to linearly increase with We, demonstrating that the rising movement in crown evolution gradually enhances with We. These results are helpful for further investigation on the droplet impact on an immiscible liquid layer.     

单液滴正碰球面动态行为特性实验研究

在考虑空气阻力影响,确定液滴撞击球面速度的基础上,对较高韦伯数液滴撞击干燥球面动态行为过程进行了实验研究,分析了球面曲率与韦伯数对液滴撞击行为和铺展因子的影响,并与前人撞击平面结果进行了对比.实验表明,靠近撞击球面时,液滴降落速度出现明显波动;球面曲率对液滴撞击后行为影响明显,曲率较大时,液滴撞击后铺展液膜会超出球面直径并滑落,曲率较小时,液滴撞击后在球面上呈现明显的铺展、回缩、震荡、着附动态变化行为,此时最大铺展因子受曲率影响小,随曲率减小,逐渐趋向于撞击平面时的最大铺展因子;韦伯数对液膜铺展速率影响较小,但对液膜回缩时间影响明显,最大铺展因子随韦伯数增加逐渐增大,获得的关联式呈指数变化.     

有序信息在空间立方体抽样中的拓展研究

在空间调查领域中,分布良好的样本中很少会同时出现彼此接近的单元.将地理坐标作为平衡变量的立方体法存在无法捕捉总体单元的空间依赖性的不足.文章在立方体法能有效捕获总体空间趋势的基础上,创新性地引入系统抽样的思想.文章提出的抽样设计方法在保持单元空间相对位置的同时,充分利用地理坐标信息,集中相似单元点获得有序总体,使原先总体具有“空间趋势”.首先,在保持空间相关性的前提下,将抽样单元排序问题转换为单源最短路径问题.然后,利用Dijkstra算法获得有序总体,在快速立方体法的飞行阶段更新初始包含概率进行有序空间抽样.最后,通过模拟研究和实证分析表明对空间总体按照相似单元彼此靠近的原则进行排序,可减少抽样误差,获得较为均衡的样本,从而验证所提抽样思路的可行性.