CFD Simulation of trasient phenomena on gas entrainment

Nishimura, Motohiko*; Nonaka, Yoshiharu*; Maekawa, Isamu*

Sodium cooled FBR reactor in a feasibility study on commercialized fast reactor system has been designed so compact that flow velocity is much higher in the reactor than in the reactors so far. This design requires an evaluation method for gas entrainment from reactor free surface and effective countermeasures. Focusing on the establishment of gas entrainment evaluation method based on CFD, CFD simulation has been carried out with analyses of an existing gas entrainment experiment. In the analyses, four turbulence models such as standard k-e, RNG k-e, non-linear k-e and k-w have been applied and evaluated for their analytical capability in addition to laminar model. Main results have been obtained as follows;1) Laminar model shows faster vortices behavior accompanied with strong flow and pressure fluctuations including random variations than any other turbulence models. RNG model shows the solutions more similar to the laminar model than the other turbulence models.2) k-w, non-linear k-e and Standard k-e models show milder vortices behavior in this order due to excess turbulence viscosity.3) Main characteristics of major turbulence models have been obtained when they are applied to gas entrainment analysis.