二、元流和总流的连续性方程( continuity equation of filament and total fiow)(量守恒定律 law of energy conservation) P,u,dA=p2u2dA, P,u, 恒定总流连续性方程( continuity equation of steady total flow) 41=5=9苦二、元流和总流的连续性方程(continuity equation of filament and total flow)(质量守恒定律law of energy conservation) 恒定总流连续性方程(continuity equation of steady total flow): A1 1 = A2  2 = Q 1 u1 dA1 = 2 u2 dA2 1u1  2u2