Compressible Flow Free Textbook

Next: Entrance Mach number, M1, Up: The Pressure Ratio, P2/P1, Previous: Fanno Flow Short 4fL/D Index

Long 4fL/D

In the case of $\frac{4fL}{D} > \left.\frac{4fL}{D}\right\vert _{max}$ reduction of the back pressure results in the same process as explained in the short $\frac{4fL}{D}$ up to point

. However, point c in this case is different from point c at the case of short tube $\frac{4fL}{D} < \left.\frac{4fL}{D}\right\vert _{max}$ . In this point the exit Mach number is equal to 1 and the flow is double shock. Further reduction of the back pressure at this stage will not ``move'' the shock wave downstream the nozzle. At point c or location of the shock wave, is a function entrance Mach number,

and the ``extra'' $\frac{4fL}{D}$ . The is no analytical solution for the location of this point c. The procedure is (will be) presented in later stage.

**Figure:** Mach number as a function of 4fL/D (total 4fL/D=0.3)
$\begin{figure}\centerline{\includegraphics {calculations/fannoMfldShockPP}} \end{figure}$

Next: Entrance Mach number, M1, Up: The Pressure Ratio, P2/P1, Previous: Fanno Flow Short 4fL/D Index

Created by:Genick Bar-Meir, Ph.D.
On: 2007-11-21