简介：Therelationbetweengrain-sizedistributionofthebedandinsuspensionwascriticallyexaminedunderauniformflowvelocityof50cm/sovertwobeds:oneofmainlyfinesandsandtheotherofmediumsands.Twosections-one2.85mdownstreamandtheother6.35mdownstreamintheexperimentalchannel-wereselectedforsamplingtostudythegrain-sortingpatternintheverticaldirectionalongthedirectionoftransport.Theshapeandtypeofthegrain-sizedistributionpatternwerecriticallystudiedwithheightabovethebed.Thechangeinthedistributionpatternhasbeenattributedtothechangeoflocalbedroughnesscausingscouringagainsttheprotrudedrelativelycoarsegrainsonthebed.Suchtrendsareimportanttopredictthenatureofriverbedtopography.ThesandofBed-1initiallyexhibitsalog-skew-Laplacedistributionatdifferentheightsofsuspension.Thedistributionpattern,however,changesbutthischangingpatternisnotconsistentalongtheupstreamside.ForBed-2,whichinitiallyexhibitsalog-normaldistribution,thesamepatternpersistsfromtheheightofsuspensionat5cmupto20cm.Suchconsistencyinlog-normalityisalsoobservedatthedownstreampointsofmeasurement.Itisgenerallyexpectedthatthemeangrain-sizewouldreducewithincreasesofsuspensionheightbuttheresultsoftheexperiments,insomeoccasions,differsignificantlyfromthegradualfiningupwardtrend.Thisresulthasbeenattributedtolocalchangesofbedroughnessarisingfromtheprotrudedrelativelycoarsegrainscausingeddies,scouring,andturbulentphenomenawhichmovescoarseparticleshigherinsuspensionaddingacoarsetailtothedistributionincreasingthemeangrain-size.