【名词&注释】
可压缩(compressible)、非定常流动(unsteady flow)、机械能守恒(conservation of mechanical energy)、当量粗糙度、总机械能(total mechanical energy)
[单选题]下列说法中,正确的说法是()
A. 理想不可压均质量重力流体作定常或非定常流动时,沿流线总机械能(total mechanical energy)守恒
B. 理想不可压均质重力流体作定常流动时,沿流线总机械能(total mechanical energy)守恒
C. 理想不可压均质重力流体作非定常流动时,沿迹线总机械能(total mechanical energy)守恒
D. 理想可压缩重力流体作非定常流动时,沿流线总机械能(total mechanical energy)守恒