On complete rebound of liquid droplets impacting on soft hydrophobic surfaces
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摘要: 采用高速摄影与图像识别技术，研究了不同黏性液滴撞击不同弹性模量的柔性疏水材料（PDMS）表面后的完全反弹过程，获得了液滴黏性和柔性疏水材料弹性模量对液滴发生完全反弹的韦伯数区间和反弹恢复系数的影响规律。结果表明：由于液滴黏性对液滴铺展过程的速度影响及其所导致的黏性能量耗散差异，当液滴黏性增大时，液滴撞击PDMS表面后发生完全反弹的最大/最小韦伯数均增大、反弹恢复系数减小；随着PDMS弹性模量的降低，液滴撞击PDMS表面后发生完全反弹的最大韦伯数增大、最小韦伯数减小，PDMS弹性模量对反弹恢复系数无明显影响。Abstract: With the method of high-speed camera and image recognition, the complete rebound of the liquid droplet with different viscosity impacting on the surface of the soft hydrophobic material (PDMS) with different elastic modulus was obtained. The influence curves of liquid viscosity and PDMS elastic modulus on the rebound Weber number and recovery coefficient of the droplet were also plotted. Due to the influence of liquid viscosity on the spreading process and viscous energy dissipation, the maximum and minimum Weber numbers of droplet complete rebound on PDMS surfaces increase with the increase of droplet viscosity, and the rebound recovery coefficient gradually decreases. With the decrease of the elastic modulus of PDMS, the maximum Weber number of droplet complete rebound on PDMS surface increases and the minimum Weber number decreases, and the elastic modulus of PDMS has no significant effect on the rebound recovery coefficient.
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Key words:
- droplet /
- PDMS /
- complete rebound /
- viscosity coefficient /
- Weber number /
- rebound recovery coefficient
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图 1 储能模量和耗能模量实验曲线
Figure 1. Curves for frequency dependence of storage modulus and loss modulus
图 4 3种液滴撞击4种PDMS表面的完全反弹韦伯数区间
Figure 4. Weber number range of three droplets rebound on four PDMS surfaces
图 5 最大反弹韦伯数下液滴撞击PDMS表面
Figure 5. Droplets impact on PDMS surfaces under maximum rebound Weber number
图 6 3种液滴撞击不同PDMS表面发生完全反弹的恢复系数与韦伯数关系
Figure 6. Weber number and recovery coefficient of three droplets rebound completely on different PDMS
图 8 液滴撞击4种PDMS表面发生完全反弹的恢复系数与韦伯数关系
Figure 8. Weber number and recovery coefficient of different droplets rebound completely on four PDMS
表 1 PDMS样品力学参数（ω = 1 rad/s）
Table 1. Elastic modulus of PDMS（ω = 1 rad/s）
No. Ratio $ G' $/kPa $ G'' $/kPa 1 10∶1 320.00 14.90 2 20∶1 120.00 11.70 3 30∶1 34.20 2.82 4 40∶1 24.00 1.29 
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表 2 实验液滴的基本参数
Table 2. Parameters of liquid droplets
No. Liquid
dropletsGlycerol
/(wt%)$ \gamma $
/(mN·m−1)$ \rho $
/(kg·m−3)$ \mu $
/(mPa·s)1 DI Water 0 72.1 998 1.01 2 Mix–1 30 71.7 1056 2.50 3 Mix–2 60 68.8 1150 10.8
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