In-bore velocity measurements in the wake of a subsonic projectile

Attention is given to an experimental apparatus for the measurement of pressure and velocity behind a projectile travelling in a tube and propelled by compressed gas, thereby simulating interior ballistics for the case of nonreacting flow with projectile velocities of up to 21 m/s. It is found by these means that the flow at any given time in the ballistic cycle is nearly one-dimensional, apart from thin regions near the wall boundaries; in all cases, the boundary layer thickness is less than 1 mm, or about 1 percent of the bore.