Influence of wettability and surface tension on bubble formation from a needle

Abstract The multiphase flow accompanied by contact line motion is a common flow phenomenon in nature and industry. When investigating the bubble formation from a needle, it is generally assumed that the contact line is fixed at the inner diameter of a needle. Namely, the influence of contact line motion on bubble formation is ignored. In this paper, the effects of wettability and surface tension on the characteristics of bubble formation were studied using volume of fluid method. The changes of bubble volume, instantaneous contact angle, contact line radius, and the motion mechanism of contact line were analyzed in detail. It is found that when surface wettability and/or surface tension are different, the motion type of contact line during bubble formation is different, and the stage of bubble formation shows a great difference too. The motion of contact line is mainly affected by the pressure inside a bubble, the adhesion force, and the hydrostatic pressure of liquid outside a bubble. The sum of all forces driving contact line to move inward or outward controls the motion type of contact line.