粗糙管中粘性流动的压降:量纲分析一般步骤 M:a+1=0 L:-3a+b+C-1=0 T:-b-2=0 解得:a=-1,b=-2,c=0 1Ap=Eu(欧拉数,1/2是人为加上去的) ②Ⅱ2=pbbc 0L0T0=(ML-3)a(L7)bLc(ML-171)
[例B5.2.2] 粗糙管中粘性流动的压降：量纲分析一般步骤 − − = − + + − = + = : 2 0 : 3 1 0 : 1 0 T b L a b c M a 解得： a = -1 , b = -2 , c = 0 1 2 1 2 p Π Eu ρV = = （欧拉数，1/2是人为加上去的） ② П2 =ρa b b c cμ M 0 L 0 T 0 = (M L – 3 ) a (L T –1 ) b L c (M L – 1 T – 1 )
粗糙管中粘性流动的压降:量纲分析一般步骤 M:a+1=0 L:-3a+b+c-1=0 解得:a=b=c=-1 (雷诺数) pva Re ③∏3=pVhd MLUTU-(MLS(LTbLCL 解得:a=b=0,c
[例B5.2.2] 粗糙管中粘性流动的压降：量纲分析一般步骤 − − = − + + − = + = : 1 0 : 3 1 0 : 1 0 T b L a b c M a 解得：a = b = c = -1 Re 1 2 = = Vd (雷诺数) ③ П3 =ρ a V bd c ε M 0 L 0 T 0 = (M L – 3 ) a (L T –1 ) b L c L 解得：a = b = 0， c = -1