」(pods 」(pos) -(P2)(A2)=-p2A2 (P1)(-A1)=P1A1 Control surface S Control volume y A1 A (pds) (pds)=-pda Fig 10.5 Finite control volume for quasi-one-dimensional flowFig.10.5 Finite control volume for quasi-one-dimensional flow ( ) 1 1 1 1 ( p )( A ) p A p x = − − =  A1 - d S ( ) 2 2 2 2 ( p )(A ) p A p x = − = −  A 2 - d S    − = − − = 2 1 2 1 ( ) A A A A A x pdS pdA pdA u l ( pdS) x = −pdA ( ) 的积分:  S x - pd S α dA α dS dS