Basics of GAS DYNAMICS P M V Subbarao Associate Professor Mechanical Engineering Department I I T Delhi Alphabets of this new literature called Gas Dynamics

c High pressure and High temperature fluid in closed tank. Role of Sonic Velocity in Engineering Stagnation Conditions. c

Role of Sonic Velocity in Engineering wc c+w c-w w Velocity of sound at any give flow velocity w.

Role of Sonic Velocity in Engineering w c+c c-c w Velocity of sound when flow velocity w=c. Define this critical parameter Velocity of sound, c

Choking of Nozzle Extent of Valve Opening

Moving Disturbance In A Fluid As an object moves through a fluid medium it creates pressure waves. Pressure waves travel out at the speed of sound which in term depends on gas properties and temperature (more on this later). If the object is traveling significantly slower than sonic velocity, then pressure waves travel out uniformly similar to waves on the surface of a pond.

Moving Disturbance In A Fluid As the object approaches the speed of sound, it begins to catch up with the pressure waves and creates an infinitesimally weak flow discontinuity just ahead of the aircraft

Moving Disturbance In A Fluid As the vehicle breaks the speed of sound, the infinitesimally weak Shock waves begin to add up along a “Mach Line” and form a strong pressure wave with highly compressed air, called a shockwave.

Moving Disturbance In A Fluid As Mach number increases, the strength of the shock wave increases and the Angle of the shockwave becomes increasingly severe Mach Angle Credit: Selkirk College Professional Aviation Program