Effect of Gravity on Contact Angle Hysteresis

Abstract

The effect of gravity on the stability of equilibrium of a fluid interface in contact with a rough and heterogeneous solid surface is studied for a system with cylindrical symmetry. The equilibrium contact angles measured in relation to the mean solid surface are then evaluated and contact angle hysteresis is discussed. The general effect of gravity is to decrease contact angle hysteresis. The effect depends on the size (width) of the fluid interface. As the size of the fluid interface decreases, it may happen that the advancing contact angle becomes smaller than the receding angle (contact angle inversion). There is also an effect of inclination of the solid surface on hysteresis. The hysteresis behaviour is predicted in detail in limiting cases and by considering a solid surface with sinusoidal grooves.