The CFD calculation of a stratification break-up test of light gas in a closed vessel

During the course of a hypothetical severe accident in a light water reactor, spray systems could be used in the containment in order to prevent overpressure in case of a steam line break and to enhance the gas mixing in case of the presence of hydrogen. Thus these two effects induced by spray might compete with each other having an influence on the hydrogen risk. Focusing on the dynamic effect of spray, the impact of spray on the break-up of a light gas layer in a closed vessel is simulated and the experimental test evaluated here is TOSQAN 113 test that belongs to the dynamic part of SARNET FP6 benchmarks. ANSYS FLUENT 14.5 is chosen for the simulation tool and spray droplets are tracked with using the Euler-Lagrange approach-Discrete Phase Model (DPM). The code validation and several sensitivity studies are done to sum up the basic method of numerical simulation of spray with CFD code and assess the influence of calculation settings and parameters, such as turbulence model and spray boundary condition. The code validation shows that the results of calculations acceptably agree with the experimental data and the sensitivity studies reveal that spray boundary condition is a rather important factor for the accuracy of simulation. Conclusion gained in from the present work can provide some reference of the numerical analysis of containment. (author)