r=c时,=0→c=4p 70 = r=0时、,州N lo L·2mlr 2 Ll /2 32L v→h 321 maX rd2
2 0 0 4 0 r J r r u c = 时， = = ( ) 4 2 2 0 r r J u = − 2 max 0 4 0 r J r u u = 时， = = 2 2 0 0 0 8 2 0 r J r u rdr A udA A Q v r A = = = = v = umax / 2 v rd l v h rd J 2 f 2 32 32 = =
达西一魏斯巴哈公式( Darcy-Weisbach equation) h=a d 2g 4R2 64 2 Re λ—沿程阻力系数,沿程水头损失 系数( Friction factor) 2 返回 A
达西—魏斯巴哈公式（Darcy-Weisbach equation）： ——沿程阻力系数，沿程水头损失 系数（Friction factor） R g l d g l hf 2 4 2 2 2 = = Re 64 = 2 3 3 = = r A u dA A 返回