Surface acoustic waves as control actuator for drop removal from solid surface

Several types of research are performed on flow control and this fact highlights the importance of this topic. Over the last two decades, actuators based on acoustic waves have attracted much attention and have been used in widespread applications from mixing to pumping. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of a sessile drop in order to change the flow characteristics. For this purpose, the removal of water from surfaces and drop movement against gravity are considered. Flow dynamics is simulated using lattice Boltzmann method. The results show that the drop can be removed from the surface in a short period of time (about one-tenth of the normal time) without moving upstream. In the microgravity condition, the dynamical behaviors of drop are affected by Bond number. There is a critical Bond number, when the Bond number is less than this parameter, drop slides on the wall. In this situation, when the wave amplitude is set to be 2.5 nm, the drop is pinned to the wall. If the wave amplitude is increased, the drop moves against gravity. Also, when the Bond number is greater than its critical value, we only can stop or remove the drop using the SAW.