[Julian121]

I am doing a simulation of an axial flow compressor by CFX.

I have a set of experimental data to validate the solution.

The ambient pressure has been measured by a barometer, but the pressure at the inlet is not known. It is assumed that the pressure at inlet is equal to the ambient pressure, though.

Is it reasonable to assume this pressure as total pressure at inlet while there exists a velocity at inlet and there is no velocity in ambient?

Shouldn’t they be different in general?

[ghorrocks]

If the stagnation pressure at your inlet is the ambient pressure - that is, there are no significant losses between the stationary atmosphere and your inlet - then the total pressure inlet with ambient pressure is the correct choice.

[sheaker]

Hello.
In my opinion it is not best idea to use pressure at both - inlet and outlet boundaries. I think that the better choice would be to combine mass flow and pressure BC's.

I was doing axial turbine simulation in CFX for my master thesis and I was using mass flow at inlet BC and static pressure at outlet BC. In Your case I would try total pressure at inlet and mass flow at outlet.


If there are parts of inlet that are not included in Your geometry (e.g inlet bell mouth) You should calculate/estimate total pressure drop in between ambient and Your inlet BC. Sometimes they can not be neglected.



Best regards,
Oskar

[Julian121]

Originally Posted by sheaker

Hello.
If there are parts of inlet that are not included in Your geometry (e.g inlet bell mouth) You should calculate/estimate total pressure drop in between ambient and Your inlet BC. Sometimes they can not be neglected.

Would there be any total pressure drop between ambient and inlet?

[ghorrocks]

There are always losses. A sharp edged entry will have quite a bit of losses, a bell-mouth opening will have very small losses. But there will always be some loss.

Whether that loss is significant depends on what you are modelling and how accurate you need to be.