Phase transition modeling

Phase-transitional flow, in particular flow with boiling and/or condensation, plays a role in many applications relevant in process technology and is therefore an important topic of research in the group. In order to be able to perform numerical simulations of these flows, the rate of mass transfer over the interface should be known. In simulation software the mass transfer rate is usually modeled by means of kinetic theory, which is not accurate in most applications. Moreover, break-up and coalescence of bubbles (like in the movie below) or droplets is usually determined by the numerical method and not by physical considerations.

Both problems can be tackled by considering the interface between the liquid and vapor phase as diffuse and incorporating intermolecular forces in the governing equations. This leads to the diffuse interface model (DIM). The drawback of DIM is that the width of the interface is so small that this model can only be applied for micro-scale simulations. Therefore, ways are studied to incorporate this model in a multi-scale approach, where single-phase flow models are applied at the macro-scales and DIM at the micro-scales.

By a combined experimental and numerical approach models are developed that describe phase-transitional flows in several applications, such as cooling of steel plates by water jets and flow regime maps in boiling flows.