# Sound barrier Giorgi Matsaberidze Sound Sound is a

• Slides: 12

Sound barrier Giorgi Matsaberidze

Sound • Sound is a vibration that travels through all forms of matter: gases, liquids, solids, and plasmas as a wave. • The matter that supports the sound is called the medium. • The speed of sound is variable and depends on the medium through which the wave is traveling.

Speed of sound Tab. 1: Speed of sound in gases (m/s) Azote Ammonia Acetylene Hydrogen 334 415 327 1284 Air Helium Oxygen Methane Chlorine 331, 46 965 316 430 206

Mach number • quantity that defines how quickly a vehicle travels with respect to the speed of sound. - the ratio of the vehicle's velocity (V) divided by the speed of sound at that altitude (a). • an aircraft flying at Mach 0. 8 is traveling at 80% of the speed of sound while a missile cruising at Mach 3 is traveling at three times the speed of sound.

Sound barrier – some definitions • Subsonic speed – slower than the speed of sound. • Supersonic speed – faster than the speed of sound. • Sound barrier - going from subsonic to supersonic speeds.

Sound barrier • The first man to break the "sound barrier" was Capt. Chuck Yeager, on 14 October 1947 on Bell XS-1, later renamed the X-1

The keys to reach the Mach 1 • minimize the increase in wave drag at transonic speeds. • develop engines with enough power • understand the effect of shock waves on wings and control surfaces so that control problems could be avoided

Wave drag • As an aircraft approaches the speed of sound, shock waves are generated along the surface. They cause the wave drag.

Wave drag • On the limit of the shock wave the properties of the stream suffer cardinal changes – its speed relating to the body decreases and becomes subsonic, pressure in the stream and the temperature of the gas increase a lot. A part of kinetic energy of a stream turns to internal energy of gas. All these changes are the more prominent, the greater is the speed of a supersonic stream. • At supersonic speeds (10 -30 M) the temperature of the gas reaches several thousand degrees that creates serious problems for devices, moving with such speeds, (for example, Space the Shuttle "Columbia" crushed on February, 1 st, 2003 because of damage of thermodefending environment, arisen during flight).

Wave drag • While retreating from the device, the front of the shock wave gradually takes almost correct conic form, pressure difference on it decreases and the shock wave turns in sound. α - the angle between the axis and the generatrix of the cone

Prandtl-Glauert singularity • the point at which a sudden drop in air pressure occurs, and is generally accepted as the cause of the visible condensation cloud that often surrounds an aircraft traveling at transonic speeds (mach 0. 8– 1. 2).

Thrust. SSC – super sonic car • developed by Richard Noble, Glynne Bowsher, Ron Ayers and Jeremy Bliss • on October 15, 1997, when it achieved a speed of 1, 228 km/h