雷諾數(shù)計(jì)算vDRe其中D為物體的幾何限度（如直徑）對于幾何形狀相似的管道，無論其 p、v、D、n如何不同，只要比值 Re相同，其流動情況就相同泊肅葉公式RlRlP1，P2管的長度兩端壓強(qiáng)流體的粘度2rldv0

drQvP1PQvP1P28lP1P2Qv8lR4薩瑟蘭公式ViscosityingasesarisesPrinciPallyfromthemoleculardiffusionthattransportsmomentumbetweenlayersofflow.Thekinetictheoryofgasesallowsaccuratepredictionofthebehaviorofgaseousviscosity.Withintheregimewherethetheoryisapplicable:ViscosityisindependentofpressureandViscosityincreasesastemperatureincreases.JamesClerkMaxwellpublishedafamouspaperin1866usingthekinetictheoryofgasestostudygaseousviscosity.(Reference:J.C.Maxwell,"Ontheviscosityor

internalfrictionofairandothergases",PhilosophicalTransactionsoftheRoyalSocietyofLondon,vol.156(1866),pp.249-268.)EffectoftemperatureontheviscosityofagasSutherland'sformulacanbeusedtoderivethedynamicviscosityofanidealgasasafunctionofthetemperature:where:n=viscosityin(Pa s)?atinputtemperature Tn=referenceviscosityin(Pa s)atreference?temperature0T=inputtemperatureinkelvinT0=referencetemperatureinkelvinC=Sutherland'sconstantforthegaseousmaterialinquestionValidfortemperaturesbetween0< T<555Kwithanerrorduetopressurelessthan10%below3.45MPahelium79.427319helium79.427319Sutherland'sconstantandreferencetemperatureforsomegasesGasC[K]T0 n0[K] [10-6Pas]air120291.1518.27nitrogen111300.5517.81oxygencarbondioxide240127292.2520.18293.1514.8carbonmonoxide118288.1517.2hydrogen72293.858.76ammoniasulfurdioxide416370293.159.82293.6512.54ViscosityofadilutegasTheChapman-Enskogequationmaybeusedtoestimateviscosityforadilutegas.Thisequationisbasedonsemi-theorethicalassumptionbyChapmanandEnskoq.Theequationrequiresthreeempiricallydeterminedparameters:thecollisiondiameter(O),themaximumenergyofattractiondividedbytheBoltzmannconstant(?/K)andthecollisionintegral(collisiondiameter(O),themaximumenergyofattractiondividedbytheBoltzmannconstant(?/K)andthecollisionintegral(3(T*)).%XID7=266.93T*=KT/￡Reducedtemperature(dimensionless)n0=viscosityfordilutegas(uP)M=molecularmass(g/mol)T=temperature(K)o=thecollisi