Numericalsimulationofflowsintight-latticefuelbundlesOriginalResearchArticle

Theflowintightrodbundlesischaracterizedbylong-term,large-scalecoherentpatternsinthestream-wisedirection. Inthepresentwork,theissueofsimulatingthesestructuresthroughunsteadyCFDsimulationsemployingperiodicboundaryconditionsinthestream-wisedirection,willbeaddressed.Thevalidityoftheapproachisassessedthroughthecomparisonofalargeeddysimulation(LES)forsimilarflowconditionsinsideasimplifiedgeometryandexperimentaldata. Apowerfulstatisticaltool(properorthonormaldecomposition)isusedtoanalyzethetimevaryingsolution.Theflowfieldhasbeendecomposedintoaseriesofnormalmodes,identifyingthestructuresresponsiblefortheflowtransferbetweensub-channels.Additionalinsightsonthephysicsofthesecoherentstructuresareobtained. AnunsteadyReynoldsaveragedNavier–Stokessimulation(URANS)oftheflowinarodbundlehasthenbeencarriedout.Thecomparisonbetweennumericalresultsandexperimentalresults[Krauss,T.,Meyer,L.,1998.Experimentalinvestigationofturbulenttransportofmomentumandenergyinaheatedrodbundle.Nucl.Eng.Design180,185–206]provesthataccuracycanbeachievedforaveragedstatisticssuchasstream-wisevelocity,turbulentintensityandwallshearstresses.