Kinetic-energy mass, momentum mass, and drift mass in steady irrotational subsonic flows

Irrotational flows caused by a body moving with a constant velocity in an unbounded homentropic compressible fluid at rest at infinity are considered. Provided the (steady) flow relative to the body is everywhere subsonic, it is shown that the momentum mass is always equal to the drift mass, and the kinetic-energy mass is equal to the drift mass under certain conditions.