动力传递与流动阻力导论（优选）第五节动力传递与流动阻力导论（动量浓度）在涡流动量通量里【VelocityDistributioninPipe(流体在圆管内的速度分布)】ForTurbulentFlow管内流动阻力的分类计算直管阻力的通式Whenfluidflowsinahorizontalandequal-diameterstraightpipe,ΔpisnumericallyequaltotheresistancelossΔpfcausedbyinternalfriction(内摩擦力).generalformulaofcalculationofstraightpiperesistance,calledFanningequation(范宁公式)λ—frictioncoefficient,dimensionless,it’srelatedtotheflowpatternandroughnessofpipewall.letr=0totalflowinpipe圆管内的湍流Ⅱ.ForturbulentflowThevelocitynearthewalldropssuddenly.pipewallconditionisrepresentedinroughness.Moodyplot(摩擦系数图—莫迪图)foranannularfluiddifferentialunitwiththicknessdronintegrating若选贮槽液面为1-1′截面，管出口外侧为2-2′截面：u2=0dimensionequation(因次方程)λisalsoindependentofevalueReplacecircularpipediameter(d)withequivalentdiameter(de)pipewallconditionisrepresentedinroughness.Replacecircularpipediameter(d)withequivalentdiameter(de)Fanningfrictionfactor(范宁摩擦因子)Fanningfrictionfactor(范宁摩擦因子)ForLayerFlowThevaluesofK,b,kandqneedtobedeterminedthroughtheexperiments.totalflowinpipe5mm与φ56×3mm。Exampledimensionequation(因次方程)ThevaluesofK,b,kandqneedtobedeterminedthroughtheexperiments.②Guyuzhenformula(顾毓珍公式)非圆形直管的摩擦阻力边界层与局部阻力的概念边界层(boundaryLayer)ForLayerFlowfundamentalphysicalquantities—mass,lengthandtimeThedistributionofvelocityisparabolicintheradialdirection.5mm与φ56×3mm。Thevelocityhasthelargestvalueatthepipecenter.WhereN=n–m,m—numbersofthefundamentaldimensiontotalflowinpipegeneralformulaofcalculationofstraightpiperesistance,calledFanningequation(范宁公式)τs—fluidshearingstrengthatthewallτisrelatedtotheflowpattern.pipewallconditionisrepresentedinroughness.velocitydistributioninlayerflowλ—frictioncoefficient,dimensionless,it’srelatedtotheflowpatternandroughnessofpipewall.因而，流动阻力产生的大小与流体的性质、流动类型、流过距离、壁面形状等有关。Newton'slawofviscosityoppositedirectionforanarbitraryfluiddifferentialunitwithlengthLandradiusr,itsforceanalysis②突然缩小【例】用泵将贮槽内1100kg/m3的液体送入表压为0.2MPa的高位槽中，管出口处高于贮槽液面20m，输送管道为φ68×4mm钢管，送液量30m3/h，溶液流经全部管道的能量损失为120J/kg(不包括出口)，求泵的轴功率（泵的效率为65