4. Conclusions
The experimental study on the impact of a water drop with additives on different wood surfaces has been performed. Following conclusions can be drawn: 1) The additives being considered obviously affect the critical Weber number for drop splash when it impacts upon wood surfaces, the smaller the drop surface tension is, the larger the critical Weber number will be. 2) The impact splash of a water drop with additives is obviously influenced by the roughness of the wood surfaces, i.e., Wec increases as Ra decreases. 3) The empirical models on predicting the critical Weber number and maximum spread factor just partially agree with the experimental results of a pure water drop and the water drop with 5% NaCl additive. The current results are limited to the interaction of a single water drop impacting upon a horizontal wood surface, and future study would be focused on improving the model by considering the effects of not only the drop liquid properties, but the surface roughness, wettability, temperature and basic density of the wood surfaces, etc.
