Many physical situations, e.g., oil droplets in water, or blood cells in blood plasma, can be modeled as a mixture of two immiscible, incompressible fluids with an interface between the fluids. Such problems are typically modelled by the incompressible Navier-Stokes equations, which describe the fluid flow, coupled with a model for the evolution of the interface between the fluids. One example of such a model is the level set method, where the interface is tracked implicitly via a scalar level set field. The location of the interface is determined by the zero contour of the level set field. The scalar level set field, and thus also the interface, is moved according to the local fluid velocity.
Using the finite element method to discretize the resulting system of partial differential equations allows for flexibility with respect to the geometry and adaptive mesh refinement. In order to accurately simulate realistic problems in 3D, millions or even billions of degrees of freedom can be required. In this case, efficient parallel implementations for large-scale computer systems are necessary