Study of the process of metal droplets with high surface tension impinging on wall

Abstract

The behavior of aluminum droplets impacting a wall critically affects the operation of solid rocket motors. In the present study, the flow and rebound of aluminum droplets with a high surface tension are studied experimentally and numerically. In addition, the impact of aluminum droplets at different inclined angles is monitored experimentally. When the droplet is about to rebound away from the wall, it is stretched to its maximum length. An empirical correlation formula is proposed to predict the maximum length when a droplet is about to bounce off a flat plane. The velocity and pressure distributions of a droplet flowing over a flat plane and an inclined plane are compared by using the volume of fluid method. Furthermore, the restitution coefficient of the droplet is discussed in detail. When normal Weber number [Formula: see text] ranges from 0 to 20, normal restitution coefficient [Formula: see text] ranges from 0.3 to 0.6. When tangential Weber number [Formula: see text] <10, tangential restitution coefficient [Formula: see text] is subject to great uncertainty. When 10 < [Formula: see text] < 80, [Formula: see text] is maintained at 0.75. The formulas for the total restitution coefficient, normal restitution coefficient, and tangential restitution coefficient of the aluminum droplets are also presented. Based on the principle of conservation of energy, we calculate the remaining energy of the aluminum droplets impinging on a wall and provide the relationship between the restitution coefficient and the dissipated energy. The results elucidate the mechanisms at work when aluminum droplets collide with a wall.