Effects of Reynolds number on stack plume trajectories simulated with small scale models in a wind tunnel

An analysisoftheeffectofReynoldsnumberonplumetrajectoriessimulatedatsmallscaleinawind tunnelispresented.ResultsdemonstratethattheReynoldsnumberofflowleavingthestack(Re)D could be criticalinspecificsimulations.Inthecasestudied,when(Re)D is around2196theexitvelocityprofile in thecylindricalstackisdistortedrelativetofullscale,orhighmodel(Re)D scenarios(i.e. ðReÞD43000), increasing themomentumfluxinplume,thusincreasingtheheightoftheplume.Theoverestimationof plume riseleadstounderestimationofgroundlevelconcentrations;thereforethesimulationwillnotbe conservativeifusedforenvironmentalimpactassessmentpurposes.Theanalysisshowsthattheeffect of (Re)D is mainlyduetotheshapeoftheemissionvelocityprofileandimpliesthatthedetailsof the turbulentstructureofthereleasesarenotimportant.Thisislikelybecausetheturbulenceinthe plume isdominatedbyinternallygeneratedturbulencethatoriginatesfromtheinitialinteractionwith the cross-flow.ResultsindicatethatmeasurementsoftheexitvelocityprofileandtheuseoftheBriggs generalisedplumerisetheorycanfurnishareliableestimateoftheerrorsinplumeriseinducedby(Re)D in specificwindtunnelsimulations.