Abstract The airflow assisted impact of water drops on surfaces with various wettabilities is studied to understand the effect of shear force and normal imposed pressure provided by the incident airflow. Results show that the maximum spreading factor increases with the impact Weber number for the drops impacting a hydrophilic surface. For other surfaces, the spreading increases with the airflow for a given Weber number. However, the factor is observed to suddenly decrease at higher Weber numbers and airflow and for the less wetting surfaces. For the hydrophilic surface, as the drop continues spread, higher adhesive force between the drop and surface causes the rim to become thinner. The shear force pushes the rim outward. As the wettability decreases, a deceleration is observed at the early stage of spreading, forming fingers and thicker rim at the last stage. The thicker rim causes the viscous dissipation to decrease suddenly for the highest Weber number and airflow tested. The thicker rim resists the drop to spread. Detachment of the satellite drops on a hydrophilic surface increases with the airflow since the shear force increases. The normal imposed pressure applies pressure on the fingers and gives momentum to the lamella in the radial direction. A comparison of the measured maximum spreading with the one obtained from an existing model, is provided. Better comparison is found for the cases of less wetting surfaces, whereas good comparison is observed only at higher impact Weber numbers for the hydrophilic surface.

中文翻译：

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液滴的空气辅助冲击：表面润湿性的影响

摘要 研究了水滴在具有各种润湿性的表面上的气流辅助冲击，以了解入射气流提供的剪切力和法向压力的影响。结果表明，对于撞击亲水表面的液滴，最大扩散系数随着撞击韦伯数的增加而增加。对于其他表面，对于给定的韦伯数，扩散随气流增加。然而，观察到该系数在较高的韦伯数和气流以及较不润湿的表面上突然下降。对于亲水表面，随着水滴继续扩散，水滴与表面之间更高的粘附力导致边缘变薄。剪切力将轮缘向外推。随着润湿性降低，在铺展的早期观察到减速，在最后阶段形成手指和更厚的边缘。对于测试的最高韦伯数和气流，较厚的边缘会导致粘性耗散突然减少。较厚的边缘可防止跌落蔓延。由于剪切力增加，亲水表面上的卫星液滴的脱离随着气流而增加。正常施加的压力对手指施加压力，并在径向上为薄片提供动量。提供了测得的最大扩散与从现有模型获得的最大扩散的比较。在润湿性较低的表面的情况下发现了更好的比较，而只有在亲水性表面的较高冲击韦伯数下才能观察到良好的比较。较厚的边缘可防止跌落蔓延。由于剪切力增加，亲水表面上的卫星液滴的脱离随着气流而增加。正常施加的压力在手指上施加压力，并在径向上为薄片提供动量。提供了测得的最大扩散与从现有模型获得的最大扩散的比较。在润湿性较低的表面的情况下发现了更好的比较，而只有在亲水性表面的较高冲击韦伯数下才能观察到良好的比较。较厚的边缘可防止跌落蔓延。由于剪切力增加，亲水表面上的卫星液滴的脱离随着气流而增加。正常施加的压力在手指上施加压力，并在径向上为薄片提供动量。提供了测得的最大扩散与从现有模型获得的最大扩散的比较。对于较少润湿表面的情况，发现了更好的比较，而仅在亲水表面的较高冲击韦伯数下才观察到良好的比较。提供了测得的最大扩散与从现有模型获得的最大扩散的比较。在润湿性较低的表面的情况下发现了更好的比较，而只有在亲水性表面的较高冲击韦伯数下才能观察到良好的比较。提供了测得的最大扩散与从现有模型获得的最大扩散的比较。在润湿性较低的表面的情况下发现了更好的比较，而只有在亲水性表面的较高冲击韦伯数下才能观察到良好的比较。