Pressure Boundary Condition

Matt Umbel

I am attempting to implement a pressure boundary condition in a 1-D code. For an ideal gas, I would like to specify total pressure and total temperature at the boundary and would like the boundary condition to:

1. Impose total pressure and total temperature if

the flow is entering the domain. 2. Impose total pressure as the static pressure if the

flow is exiting the domain and flow is subsonic. 3. Impose nothing (everything extrapolated from inside

domain) if flow is exiting domain and is supersonic.

This condition should represent (I believe) a plenum type pressure boundary.

I have no problem making the code follow condition (1); however, I am not sure about the implementation for (2) and (3). Some codes I have worked with have imposed this condition, though I have never seen the implementation. Does anyone know of a reference that discusses anything close to the above boundary condition? Specifically, I am looking for actual equations and information on the algorithim (as oppose to just a vague description of what to set).

Thanks, Matt