LARGE-EDDY SIMULATIONS IN NUCLEAR-REACTORS THERMAL-HYDRAULICS

Nuclear industry requires detailed computations of thermal-hydraulic p henomena in different regions of nuclear reactors. It is interesting t o know how Large Eddy Simulation method can be applied to the computat ion of turbulent flows inside a reactor vessel. The examples presented show that physical complex flows become accessible to the simulation: confined mixing layers, stratified shear flows, externally excited tu rbulent jets. In all cases, correct predictions were obtaines for velo city and thermal fields statistics (mean values, mean standard deviati ons, Strouhal numbers,..) and also for the dynamics of the flow (onset of instabilities, dynamics of vortices). Furthermore a better underst anding of the vortex structures should make possible the active contro l of the flow (jet spreading rate, mixing enhancement...) and develops better engineering applications.