On the validity of the two-fluid model for simulations of bubbly flow in nuclear reactors

Paper in proceeding, 2014

In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble size as well as the domain size. In addition, the predictions from the two-fluid model are compared against the results from a dense Eulerian-Lagrangian particle-in-cell model in which the motion of individual bubbles are resolved in a Lagrangian frame of reference. The results obtained in this work contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.