Abstract :
Newtrendsincomputationalmethodsfornuclearreactorthermal–hydraulicsarediscussed;traditionally,thesehavebeenbasedonthetwo-fluidmodel.AlthoughCFDcomputationsforsinglephaseflowsarecommonplace,ComputationalMulti-FluidDynamics(CMFD)isstillunderdevelopment.One-fluidmethodscoupledwithinterfacetrackingtechniquesprovideinterestingopportunitiesandenlargethescopeofproblemsthatcanbesolved.Forcertainproblems,onemayhavetoconduct“cascades”ofcomputationsatincreasinglyfinerscalestoresolveallissues.Thecasestudyofcondensationofsteam/airmixturesinjectedfromadownward-facingventintoapoolofwaterandaproposedCMFDinitiativetonumericallymodelCriticalHeatFlux(CHF)illustratesuchcascades.Fortheventingproblem,avarietyoftoolsareused:asystemcodeforsystembehaviour;aninterface-trackingmethod(VolumeofFluid,VOF)toexaminethebehaviouroflargebubbles;direct-contactcondensationcanbetreatedeitherbyDirectNumericalSimulation(DNS)orbyanalyticalmethods.
