Compressible Flow credits Logo credits
Potto Home Contact Us

Potto Home

About Potto

Chapters:

  Content
  Introduction
  Sound
  Isentropic
  Shock
  Gravity
  Isothermal
  Fanno
  Rayleigh
  Tank
  Piston
  Oblique
  Prandtl-Meyer
  Hard copy
  Gas Dynamics Tables

Other things:
Other resources
Download Area
calculators

Other Resources

  FAQs
  Compare Other Books
  Articles

Potto Statistics

License

Feedback

next up previous index
Next: Shock-Choke Phenomenon Up: General Velocities Issues Previous: General Velocities Issues   Index


Piston Velocity

When a piston is moving, it creates a shock that moves at a speed greater than that of the piston itself. The unknown data are the piston velocity, the temperature, and, other conditions ahead of the shock. Therefore, no Mach number is given but pieces of information on both sides of the shock. In this case, the calculations for Us can be obtained from equation (5.24) that relate the shock velocities and Shock Mach number as
Equation (5.64) is a quadratic equation for Msx. There are three solutions of which the first one is Msx=0 and this is immediately disregarded. The other two solutions are
The negative sign provides a negative value which is disregarded, and the only solution left is
or in a dimensionless form
Where the ``strange'' Mach number is Msx′ = Ux′ /Cx. The limit of the equation when cx⇒ ∞ leads to
As one additional ``strange'' it can be seen that the shock is close to the piston when the gas ahead of the piston is very hot. This phenomenon occurs in many industrial applications, such as the internal combustion engines and die casting. Some use equation (5.68) to explain the next Shock-Choke phenomenon.


next up previous index
Next: Shock-Choke Phenomenon Up: General Velocities Issues Previous: General Velocities Issues   Index
Created by:Genick Bar-Meir, Ph.D.
On: 2007-11-21