Prandtl–Glauert singularity

The clouds sheet effect (also called Prandtl - Glauert condensation cloud) is the appearance of a cloud of water mist with the characteristic shape of a flat cone that can be visible on missiles, moving at supersonic speed. For formations of similar phenomena may occur already at high subsonic speed when local currents on the missile to reach the speed of sound. Clouds disc consists of water droplets in the low pressure zone, which follows the front of the shock wave. In this vacuum zone, the air cools adiabatically. And characterized by the reduced air pressure of the dew point is not reached, and the water vapor condenses in the air. After the passage of the shock wave turns back to normal pressure, making the fog disappears immediately. Since the negative pressure zone on the missile is based in the rear of the missile a static phenomenon, the clouds disc seems to accompany the missile. Similar effects are also observed for pressure waves of explosions ( Wilson cloud).