Numerical investigations of closures for interface forces in dispersed flows using 3D front tracking model

Closures for the drag, virtual mass and lift forces acting on a single air bubble or toluene droplet in water have been studied using a 3D Front Tracking model. The numerical implementation of the FT model was improved to allow simulations of very small air bubbles rising in water (~1 mm) using realistic physical properties. For this system the surface tension force, density ratio and the Reynolds number all are very high. The computed drag force coefficient for air bubbles in water (1-5 mm diameter) compare reasonably well with experimental data obtained results using ultra pure water. Similar drag coefficients were computed for toluene droplets rising in water, as expected since these two systems possess comparable Morton numbers. For the virtual mass coefficient a value of 0.53 was found on a 80x80x80 grid for air bubbles in water, which compares very well with the theoretical value of 0.50. Finally, the lift force coefficient was computed for a 4 mm air bubble rising in water. A value of 0.5 was computed, which is slightly higher than reported experimentally at somewhat lower Reynolds numbers.