Shedding of salt water drops under icing conditions Available to Purchase

Keeping the interaction of sea water with the surfaces of marine vehicles in mind, the shedding of a salt water drop from a super hydrophobic surface under icing condition is studied. The surface and the surrounding were set at three different temperatures: 22, −1, and −7 °C, and a gradually increasing shear flow of air was set to provide the necessary drag on salt water drops of various sizes placed on the surface. The drop sheds when the drag just overcomes the adhesion force between the surface and the drop. The velocity of the airflow at that instant is termed as the critical velocity of shedding of a given drop. The critical velocity is found to increase with decreasing temperature. While exploring the reasons behind, it is observed that for a given drop, the contact angle hysteresis and the contact length increases as the temperature decreases. The drop flattens on the surface at reduced temperatures. Therefore, the drop surface adhesion becomes higher, needing higher drag for the shedding. So, the critical velocity becomes higher. In general, the critical velocity for a given salt water drop is higher than a normal water drop. Here again, the hysteresis is observed to be higher than a given normal water drop. For a given temperature, negligible variation in the critical velocity is observed when the volume increases for both normal water and salt water drops, i.e., the critical velocity is not dependent on the drop volume for the present case.