水成冰，冰化水200字

雷诺数计算PvDRe=n其中D为物体的几何限度（如直径）对于几何形状相似的管道，无论其p、v、D、n如何不同，只要比值Re相同，其流动情况就相同P,P12n12泊肃叶公式管的半径管的长度两端压强流体的粘度dvdr(P—P)兀r2+n2兀rl=0萨瑟兰公式Viscosityingasesarisesprincipallyfromthemoleculardiffusionthattransportsmomentumbetweenlayersofflow.Thekinetictheoryofgasesallowsaccuratepredictionofthebehaviorofgaseousviscosity.Withintheregimewherethetheoryisapplicable:ViscosityisindependentofpressureandViscosityincreasesastemperatureincreases.JamesClerkMaxwellpublishedafamouspaperin1866usingthekinetictheoryofgasestostudygaseousviscosity.(Reference:J.C.Maxwell,"Ontheviscosityorinternalfrictionofairandothergases",PhilosophicalTransactionsoftheRoyalSocietyofLondon,vol.156(1866),pp.249-268.)EffectoftemperatureontheviscosityofagasSutherland'sformulacanbeusedtoderivethedynamicviscosityofanidealgasasafunctionofthetemperature:T(}IC(T\^~J1=Vi}TTc\n)where:=viscosityin(Pa・s)atinputtemperatureT0=referenceviscosityin(Pa・s)atreferencetemperatureT0T=inputtemperatureinkelvinT0=referencetemperatureinkelvinC=Sutherland'sconstantforthegaseousmaterialinquestionValidfortemperaturesbetween0，“T=T/Reducedtemperature(dimensionless)0=viscosityfordilutegas(uP)M=molecularmass(g/mol)T=temperature(K)=thecollisiondiameter(A)=themaximumenergyofattractiondividedbytheBoltzmannconstant(K)=thecollisionintegral