Hydrodynamic Forces on a Rough Wall

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1、REVIEWSOFMODERNPHVSICSVOLUME21,NUMBER3JULY,1949::—::ycroiynaIIiic.&orcesona.doug.~Wa....HANSALBERTEINSTEINANDEL-SAYEDAHMEDEL-SAMNIBerkeley,CalzforrliaThedynamicforceswhichaturbulentQowexertsontheindividualprotrusionsofaroughwallhavebeenmeasured.Itwasfoundthateveninthecaseofanextremelyhigh

2、relativeroughness,thedragforceontheprotrusionsmaybedeterminedfromthelogarithmicfrictionlaws.AverysignificantliftforcewhichtendstopulltheprotrusionsawayfromthewallandintotheQowwasmeasured.Thisliftforcewasdividedintotwoparts;AconstantaveragevalueandarandomQuctuationsuperimposedovertheaverag

3、e.Acarefulstatisticalanalysisshowedthatthefrequencyofdiferentpressuresorliftforcesatthewallfollowsveryaccuratelythenormalerrorlaw.Thisfactseemstoindicatethatinthedescriptionofturbulenceneararoughwall,thepressuresmust,beregardedastheprimaryinQuence,notthevelocities.THEPROBLEMsystematically

4、,eithertheoreticallyorexperimentally.HEstudydescribedinthispaperoriginallywasItwasmandatory,therefore,toobtainfirstsomebasicinitiatedwiththeprimarypurposeofstudyingexperimentaldata.thedynamicforcesactingonparticlesinthesurfaceFundamentally,twodiferentapproachescanbeused:Oneistoinvestigate

5、theRowpatternaroundthelayerofasedimentbed.Thestatisticaldistributionofprotrusionsofthewallandtodescribeitbymeansoftheseforcesshouldpermitthepredictionofthefre-thestatisticalturbulencetheory.Theforcesactingonquencywithwhichsolidparticlesareremovedfromatheindividualparticlesorroughnessprotr

6、usionsofthestreambedbyagivenRow.IthasbeenshownthatthesedimentmotiononsuchabedmaybedeterminedboundarymustthenbecalculatedfromtheRowheld.Asecond,moredirect,butalsomoreempiricalapproachfromtheabove-mentionedfrequencywithwhichtheisthedirectmeasurementoftheforces.Thissecondliftforcesovercometh

7、eparticleweightinconjunctionwithanindependentstatisticaldescriptionoftheapproachwaschosenbecauseitwasbelievedtobethequickerandthemorereliableofthetwo.subsequentparticlemotion.'TheonlyexistingtheoryoftheturbulentRowpatternThispaperdealsonlywiththeforceswhichtheRowalo