Impingement of aqueous film forming foam (AFFF) solution drops on wood: Wetting and splash

Abstract

Drop impact is immensely important in many scientific principles and technological applications. Although the impact of liquid drops has been subjected to extensive experimental and theoretical work, the dynamic wetting behavior and the splash phenomenon of impinging water drops containing surfactant additives are still not clear. This study investigated the impingement of Aqueous Film Forming Foam (AFFF) solution drops on Shorea spp. The impingement of AFFF (0.03%) solution drops was captured using a high-speed video camera at different impact velocities to understand the behavior of the impinging drops, the occurrence of splash phenomenon and the characteristics of the emitted droplets. The collision dynamics of the AFFF solution drops were also compared with that of pure water drops at a similar range of impact velocities. The experimental data identified that the wetting behavior of the impinging drops and the characteristics of the emitted droplets were predominantly dependent on the impact velocity and the surface tension of the liquid drops. The formation of secondary droplets during the impingement of a water drop and AFFF solution drop was further evaluated and it was revealed that despite a substantial difference in surface tension, the formation of emitted droplets was similar to each other.