We simulated impact of water, n-heptane, and molten nickel droplets on a solid surface. A numerical code was developed to model the motion of both the liquid in the droplet and the surrounding air. The model used a volume-of-fluid method to track the droplet surface and assumed that only one flow field governed the motion of all the fluids present. Predicted droplet shapes during impact agreed well with photographs. When a droplet approached another surface, air in the gap between them was forced out. Increased air pressure below a droplet created a depression in its surface in which air was trapped. The magnitude of pressure rise could be predicted using a simple analysis of fluid between two solid planes moving closer together. The air bubble formed at the solid–liquid interface remained attached to the solid surface in a water droplet. In an n-heptane droplet the bubble moved away from the surface and broke into two or three smaller bubbles before escaping through the droplet surface. This difference in behavior was attributed to the contact angle of water being much larger than that of n-heptane.

SUMMARYThis paper presents a method to calculate heat transfer across an interface separating immiscible fluids. A volume tracking method was used to model the simultaneous movement of mass, momentum and energy across cell boundaries. Both first-and second-order methods were used to approximate temperature fields with sharp gradients that exist near the fluid-fluid interface. Temperature distributions around hot droplets surrounded by a colder fluid with uniform velocity were calculated and the magnitude of false diffusion identified. The effect of changing the thermal diffusivity of the surrounding fluid was studied. It was found that in most cases a second-order approximation, such as the van Leer scheme, is sufficient for estimating advection temperatures. To demonstrate the capabilities of the model we modelled molten tin droplets falling in an oil bath. The development of vortices behind droplets was modelled and the effect of fluid re-circulation and oil thermal conductivity on heat dissipation studied.

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This paper presents the effect of interfacial heat transfer on the breakup of an annular jet surrounded by another viscous liquid. Specifically, we consider the breakup of a molten tin jet in eicosane. One-field volume tracking is used which involves solving one set of equations for conservation of mass, momentum and energy. The original idea behind volume tracking methods has been used not only to advect mass and momentum but also energy across cell boundaries. The van Leer method is used to approximate advection temperatures across the sharp temperature gradients existing at fluid/fluid interface. To study the effect of heat transfer on the hydrodynamics of the flow, all fluid properties except density are modelled as temperature dependent. Results show a direct correlation between interfacial heat transfer and the location of the breakup. For tin, results show that the temperature dependency of viscosity is the major factor in dictating the location and time of the breakup.