What Does the Graph in My Compressive Flow Experiment Indicate?

[bortonj88]

Homework Statement

Wondering if anyone could give me a hand, I have created the attached graph. It shows the variations of pressure in the nozzle for different supply pressures and back pressures, in the form, P/Po vs position of the nozzle. and not too sure what its showing

Homework Equations

Wondering if anyone can help me figure out what the graph is showing??

The Attempt at a Solution

 

[bortonj88]

I didn't mention that the nozzle a converging- diverging nozzle. Also I know that at the throat of the nozzle the fluid cannot reach speeds above Mach 1, sonic speeds. However i am wondering where on the graph this relates too.\

I also know that the Pc/Po(critical pressure ratio) for air is 0.5283 and it seems that as the pressure difference becomes larger the closer the P/Po becomes to the critical ratio value.

Any help will be greatly appreciated as this has to be submitted by friday.

Thanks
John