Abstract
When the velocity of a body moving in air reaches a certain critical amount less than the velocity of sound, condensation and rarefaction waves are produced respectively on the head and tail surfaces of the body. The position and direction of these waves relative to the body depend on its velocity relative to that of sound in air. In an airscrew, tip condensation and rarefaction waves are also produced at the critical moment at the head and tail edges respectively of the blade tip.
In the present paper, these critical waves and the waves which are produced when the velocity of the body is greater than that of sound are dealt with. Mathematical equations useful for calculating the motion of these waves are also given, and it is made clear that the energy consumed by these waves depends on the 4th power of the velocity of the body.
