Critical contact angle for triggering dynamic Leidenfrost phenomenon at different surface wettability: A molecular dynamics study

The microscopic mechanism of the dynamic Leidenfrost phenomenon involving the impact of droplets on high -temperature surfaces remains unclear, although many efforts have been devoted to the static Leidenfrost phe-nomenon of evaporative sessile droplets. In this work, we study the dynamic Leidenfrost phenomenon of droplets impacting high-temperature surfaces with different wettability by using water and copper. The simulations by the molecular dynamics method show that determined by the atomic potential energy, a hydrophilic surface favors a lower dynamic Leidenfrost temperature compared to a hydrophobic surface. It is found that there is a critical contact angle that can trigger the Leidenfrost phenomenon at different surface temperatures. The critical contact angles are about 44.06 degrees, 87.93 degrees, and 92.63 degrees when the surface temperatures are 998 K, 1,098 K, and 1,198 K, respectively. That the critical contact angle becomes larger with elevated surface temperature is helpful for industrial designs, in which novel insulating materials with higher Leidenfrost temperatures are required.