TITLE : UNDEREXPANDED FREE JET

BY : Q Zhang - CHAM Development Team

DETAILS :

• The problem considered is an axisymmetric sonic jet discharging into stagnant surroundings at a pressure higher than the ambient pressure.

• The simulations are based on experiments of Donaldson and Snedeker (1971).

• The simulation is two-dimensional and the k-e turbulence model is used.

Pictures are as follows :

1. Pressure contours
2. Mach number contours
3. Density contours
4. Mach number distribution along the flow axis

DISCUSSION :

• The computed structure of the jet is in good accord with that observed in experiments. As the fluid leaves the nozzle, the pressure mismatch generates a rapid expansion and a down-running oblique shock wave. This shock interacts with the expansion waves returning from the flow axis to form a Mach disc.
• Details of the experiments can be found in:

A study of free jet impingement, Part 1: Mean properties of free and expanding jets Donaldson C and Snedeker R S Journal of Fluid Mechanics, Vol. 45, pp281-319, 1971.