Sensitivity Analysis on the Critical Mass Flowrate Based on Sobol’ Indices Through Replicated LHS

Abstract

International audienceIn order to quantify uncertainties of constitutive relationships in thermal-hydraulic system codes, the setup of an experimental database based on Separated Effect Tests (SET) is a critical step. Basically, series of experiments are carried out over various experimental input conditions to study some thermal-hydraulic Quantities of Interests (QoIs). Those quantities usually depend on several constitutive relationships whose individual impact should be assessed by performing a sensitivity analysis.In the paper, a sensitivity analysis based on first-order Sobol’ indices through replicated Latin Hypercube Sampling (rLHS) is proposed to identify the most influential constitutive relationships. Using rLHS allows to strongly reduce the number of simulations needed to compute the whole set of first order Sobol’ indices.A comparison between SET series will be performed. This method is applied to a database composed by two series of SETs in which the critical mass flowratesimulated with the thermal-hydraulic system code CATHARE2 is the QoI. Generally, the relevance of the constitutive relationships of the code on the QoI depends on the experimental input conditions and the geometry of the mock-up. With this study, we can shade such dependences and establish a database based on the impact of the physical models.Finally, the purposes of this analysis are to define which constitutive relationships can be judged as significant and to rank the experiments of the two SETs according to the effect of these constitutive relationships on the mass flowrate