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Effect of wettability on droplet impact: Spreading and splashing
Experimental Thermal and Fluid Science ( IF 2.8 ) Pub Date : 2021-02-08 , DOI: 10.1016/j.expthermflusci.2021.110369
Haixiang Zhang , Xiwen Zhang , Xian Yi , Feng He , Fenglei Niu , Pengfei Hao

This study experimentally investigates the dynamic behaviors of water droplets over wide ranges of diameters and velocities (200 μm < D0 < 2600 μm, 50 < We < 3000) impacting on surfaces with various wettability (ranging from hydrophilic to superhydrophobic), and focuses on the effect of surface wettability on water droplet spreading and splashing. The experimental results show that the surface wettability contributes to the lift of the lamella, related to the cosine of the advancing angle (cosθa), that significantly influence the spreading and splashing. The lifting lamella promotes the spreading speed by reducing the surface friction and the viscous dissipation in the boundary layer. The mean spreading speed is linear to the impact velocity on each surface type, and the contact angle slightly affects the mean spreading velocity on the hydrophilic or hydrophobic surface. While, the mean spreading velocity on the superhydrophobic surface is much larger than the other surfaces due to the fewer viscous dissipation. The splashing behavior is dominated by the force from the air surrounding the lamella. The experimental results demonstrate that the splashing threshold K = OhRe1.25 is independent of the advancing angle for the case of θa < 90°, but is proportional to cosθa for the case θa > 90°. Furthermore, we put forward a prediction model of droplet splashing threshold, considering the effect of surface wettability, as K/K0 = 1 + αcosθa, which could quantitatively express the effect of surface wettability on water droplet splashing.



中文翻译:

润湿性对液滴冲击的影响:扩散和飞溅

这项研究通过实验研究了水滴在各种直径和速度范围内(200μm< D 0  <2600μm,50 <  We  <3000)在不同润湿性(从亲水性到超疏水性)表面上的动力学行为 ,并着重于表面润湿性对水滴散布和飞溅的影响。实验结果表明,表面润湿性有助于薄片的电梯中,与前进角的余弦(COS θ),这会严重影响扩散和飞溅。提升薄片通过减少边界层中的表面摩擦和粘性耗散来促进铺展速度。平均铺展速度与每种表面类型上的撞击速度成线性关系,接触角对亲水或疏水表面的平均铺展速度有轻微影响。同时,由于较少的粘性耗散,超疏水表面上的平均铺展速度比其他表面大得多。飞溅行为主要受薄片周围空气的力影响。实验结果表明,该飞溅阈ķ  = 奥赫热河1.25独立于前进角为的情况下,θ <90°,但是正比于COS θ对的情况下θ > 90°。此外,我们提出液滴飞溅阈值的预测模型,考虑到表面润湿性的效果,如K /ķ 0  = 1 +  α COS θ一个,这可能定量地表达的表面润湿性的上水滴飞溅的效果。

更新日期:2021-02-16
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