Fig. 1. Schematic diagram of thin water film with surfactant on a SAW device: (a) Top view; (b) front view.放置在SAW器件上的含活性剂薄水膜示意图　(a)俯视图; (b)正视图

Fig. 2. Spreading process when the drift of mass governs the film dynamics: (a) Film thickness; (b) surfactant concentration; (c) the position of the front x_f and the rear x_r of the liquid film; (d) maximal thickness and spreading radius of the liquid film. 漂移流起主导作用, 考虑活性剂影响时水膜的铺展过程　(a)液膜厚度; (b)活性剂浓度; (c)液膜前缘x_f与后缘x_r; (d)最大厚度与铺展半径

Fig. 3. Horizontal velocity contour within the film along with streamlines at different time: (a) t = 10; (b) t = 100. 不同时刻下液膜内部的流线与水平方向分速度　(a) t = 10; (b) t = 100

Fig. 4. Film profiles at different times during the drift governed spreading process with (blue line) and without (orange line) considering the effect of surfactant.漂移流主导时, 考虑活性剂影响和不考虑活性剂影响的液膜演化过程对比

Fig. 5. Comparison between simulated and experimental^[6] results for the variation of exponent n with dimensional time during the drift governed spreading process (the variation of the position of the front of the film with time accords to the power laws x_f^*～t^*n). 漂移流主导时, 幂指数n随时间t^*的变化与Rezk等^[6]的实验结果的对比(液膜前缘位置与时间满足规律x_f^*～t^*n)

Fig. 6. Comparison between simulated and experimental^[7] results for the variation of dimensional velocity dx_f^*/dt^* with U^*2 during the drift governed spreading process 漂移流主导时, 液膜前缘移动速度dx_f^*/dt^*随U^*2的变化与Rezk等^[7]实验结果的对比

Fig. 7. Spreading process when the equal effect of drift and the capillary stress is considered: (a) Film thickness; (b) surfactant concentration; (c) the position of the front x_f and the rear x_r of the liquid film; (d) maximal thickness and spreading radius of the liquid film. 毛细力和漂移流作用相当, 考虑活性剂影响时水膜的铺展过程　(a)液膜厚度; (b)活性剂浓度; (c)液膜前缘x_f与后缘x_r; (d)液膜最大厚度h_max与铺展半径r

Fig. 8. Film spreading when both the capillary stress and the drift govern the dynamics of the film with (blue line) and without (orange line) considering the effect of surfactant: (a) Maximal thickness of the liquid film; (b) spreading radius of the liquid film.考虑活性剂影响和不考虑活性剂影响的液膜演化过程对比　(a)液膜最大厚度; (b)液膜铺展半径

Fig. 9. Comparison between simulated and experimental^[8] results for the variation of velocity dx_f/dt with θ³/We when both the capillary stress and the drift govern the dynamics of the film. 漂移流和毛细力作用相当时, 液膜前缘移动速度的模拟结果和文献[8]的实验结果对比

Fig. 10. Evolution of partially wetting film with different values of α: (a) Maximal thickness of the liquid film; (b) spreading radius of the liquid film. 不同α下部分润湿薄液膜的铺展过程对比　(a)最大厚度; (b)铺展半径

Fig. 11. Evolution of partially wetting film with different values of M: (a) Maximal thickness of the liquid film; (b) spreading radius of the liquid film. 不同M下部分润湿薄液膜的铺展过程对比　(a)最大厚度; (b)铺展半径

Table 1. Order of magnitude estimates for dimensional parameters.

Table 2. Order of magnitude estimates for nondimensional parameters.