A new model for the bouncing regime boundary in binary droplet collisions
A new model for the bouncing regime boundary in binary droplet collisions
复制标题
DOI：
10.1063/1.5085762
复制
发表时间：
2019-02
影响因子：
4.6
通讯作者：
Karrar H. Al-Dirawi;A. Bayly
中科院分区：
文献类型：
--
作者：
Karrar H. Al-Dirawi;A. Bayly
这项工作使用 2%、4% 和 8% 的羟丙基甲基纤维素水溶液，通过实验研究了相同液滴在一定液体粘度范围内的二元碰撞。使用高速摄像机捕获碰撞，并得出碰撞结果的状态图。对现有弹跳范围边界模型的性能进行了评估，发现预测结果很差。这归因于这些模型中使用的动能和液滴形状因素处理的假设和错误。导出了一个解决这些问题的新模型：修正了导致变形的动能的定义；提出了一种新的形状因子，可以准确反映最大变形时液滴的几何形状，并且重要的是，采用了一种经验方法来解释冲击参数对该形状因子的影响。此外，该模型还包括粘性耗散的估计，该估计是直接根据实验观察到的冲击动能和回弹动能之间的差异以及碰撞后液滴振荡的测量结果计算得出的。与现有模型相比，所提出的模型显示出显着的改进，将平均绝对误差降低了一个数量级。这项工作使用 2%、4% 和 8% 的羟丙基甲基纤维素水溶液，通过实验研究了相同液滴在一定液体粘度范围内的二元碰撞。使用高速摄像机捕获碰撞，并得出碰撞结果的状态图。对现有弹跳范围边界模型的性能进行了评估，发现预测结果很差。这归因于这些模型中使用的动能和液滴形状因素处理的假设和错误。导出了一个解决这些问题的新模型：修正了导致变形的动能的定义；提出了一种新的形状因子，可以准确反映最大变形时液滴的几何形状，并且重要的是，采用了一种经验方法来解释冲击参数对该形状因子的影响。此外，该模型还包括粘性耗散的估计，该估计是根据...计算的
This work experimentally investigates binary collisions of identical droplets over a range of liquid viscosities, using 2%, 4%, and 8% of hydroxypropyl methylcellulose solutions in water. The collisions were captured by using a high-speed camera, and regime maps of collision outcomes were derived. The performance of existing models of the boundary of the bouncing regime was assessed and found to give poor predictions. This was attributed to assumptions and errors in the treatment of kinetic energy and the droplet shape factors used in these models. A new model was derived which addresses these issues: the definition of the kinetic energy that contributes to deformation was corrected; a new shape factor that accurately reflects the geometry of the droplet at maximum deformation was proposed, and, importantly, an empirical approach was implemented to account for the effect of the impact parameter on this shape factor. Moreover, the model includes an estimate of the viscous dissipation, which is calculated directly from the experimentally observed difference between the impact and the rebound kinetic energies and measurements of the post-collision droplet oscillations. The proposed model shows a striking improvement versus the existing models, reducing the mean absolute error by an order of magnitude.This work experimentally investigates binary collisions of identical droplets over a range of liquid viscosities, using 2%, 4%, and 8% of hydroxypropyl methylcellulose solutions in water. The collisions were captured by using a high-speed camera, and regime maps of collision outcomes were derived. The performance of existing models of the boundary of the bouncing regime was assessed and found to give poor predictions. This was attributed to assumptions and errors in the treatment of kinetic energy and the droplet shape factors used in these models. A new model was derived which addresses these issues: the definition of the kinetic energy that contributes to deformation was corrected; a new shape factor that accurately reflects the geometry of the droplet at maximum deformation was proposed, and, importantly, an empirical approach was implemented to account for the effect of the impact parameter on this shape factor. Moreover, the model includes an estimate of the viscous dissipation, which is calculated d...