System transient include 3D phenomena Transient simulation for safety require low CPU to allow many runs for UQ Coupling between reactor circuits, containment and passive systems may be necessary Many types of 3D simulation tools exist (CFD in open medium, porous body CFD, 3D modules of system codes? Multi-1D+crossflows) with many options for physical models (e.g. turbulence model) How to select the right 3D tool depending on the objective? FONESYS Meeting, June 2020, Mixing problems are encountered in reactor thermalhydraulics which may require 3D modelling of some components: MSLB, Boron dilution, H2 mixing, PTS, passive systems,… Turbulence controls the efficiency of the mixing Buoyancy effects and density stratification may play a role Predicting turbulence mixing requires CFD with very fine nodalization in all shear layers, high order numerical schemes and needs very high CPU cost 3D models of system codes use coarse nodalization and first order numerical schemes: low CPU cost When buoyancy effects are dominant or sufficiently high, the mixing may be low and a coarse nodalization may predict the behavior rather well
Proposed activity on 3D modeling of passive systems and other mixing problems using coarse nodalization
D'Auria F.
Co-primo
Supervision
;
2020-01-01
Abstract
System transient include 3D phenomena Transient simulation for safety require low CPU to allow many runs for UQ Coupling between reactor circuits, containment and passive systems may be necessary Many types of 3D simulation tools exist (CFD in open medium, porous body CFD, 3D modules of system codes? Multi-1D+crossflows) with many options for physical models (e.g. turbulence model) How to select the right 3D tool depending on the objective? FONESYS Meeting, June 2020, Mixing problems are encountered in reactor thermalhydraulics which may require 3D modelling of some components: MSLB, Boron dilution, H2 mixing, PTS, passive systems,… Turbulence controls the efficiency of the mixing Buoyancy effects and density stratification may play a role Predicting turbulence mixing requires CFD with very fine nodalization in all shear layers, high order numerical schemes and needs very high CPU cost 3D models of system codes use coarse nodalization and first order numerical schemes: low CPU cost When buoyancy effects are dominant or sufficiently high, the mixing may be low and a coarse nodalization may predict the behavior rather wellI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.