Bubble formation and detachment on nonwetted surfaces

The shape of an air bubble generated on a horizontal flat plate with a poorly wetted surface was predicted with the finite element method. The receding contact angle determined the shape of a bubble growing on the surface by injecting air into it while the advancing contact angle determined the shape of a bubble shrinking by drawing air from it. However, the shape of a bubble just after the start of drawing air was not determined by using neither the advancing contact angle nor the receding contact angle. The attachment area of the bubble to the surface governed the shape of the bubble in this period. The bubble shape in this period was not uniquely determined by using the two contact angles. The maximum volume of a bubble just before detachment agreed with the calculated values within a scatter of±10 pct.