Meaning
Numerical methods for multiphase fluid dynamics track the position and shape of moving interfaces between immiscible fluids on a fixed grid. The volume of fluid represents a surface-tracking technique that solves a single set of momentum equations while tracking the volume fraction of each fluid in every cell. This approach is used to simulate sloshing, mold filling, spray modeling, and droplet dynamics.
It operates by defining a fraction variable that ranges from zero to one depending on the fluid content.
Transport Equation
The model solves an advection equation for the volume fraction of the primary phase using the calculated velocity field. A cell value of zero indicates that the cell is filled entirely with the secondary phase, while a value of one indicates only the primary phase. Values between these limits represent cells containing the fluid interface.
Interface Reconstruction
Maintaining a sharp interface requires specialized numerical schemes that reconstruct the boundary within partially filled cells. Linear interface calculation methods determine the orientation of the boundary using the volume fraction gradient. This reconstruction prevents the interface from artificial numerical diffusion and maintains physical clarity.
Simulation Boundary
The technique struggles to resolve droplets or bubbles that are smaller than the local grid size, which requires grid refinement or hybrid modeling approaches. This grid dependency increases the computational cost when simulating complex atomization processes.
