An experiment was carried out to study the process of pure water drop and water drop with 4% surfactant AFFF impacting on wood surfaces heated or at room temperature.The temperature of the heated wood surface was 124.7℃

while the height of the drop was varied from 15 cm to 40 cm.The initial diameters of pure water drop and the water drop with 4% AFFF were fixed at (2.4±0.1)mm and (1.8±0.1)mm

respectively.The impacting processes were recorded by using a Photron Fastcam high-speed digital camera with 2000 fps.The experimental results show that the number of splashed droplets and the maximum spread factor increase as the impacting velocity of drop increases.When the pure water drop impacts on the heated charring wood surface

it will splash many daughter drops after 4 ms and produce a big liquid column on the surface.A few milliseconds later

the water drop changes to a small liquid column and stays on the wood surface.However

the well wetting process occurs with the water drop containing 4% AFFF.