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How to properly model the inlet boundary condition to get realistic pressure values

Valued Contributor
Valued Contributor

Hi there,

 

I was wondering how to model a proper inlet pressure boundary condition.

 

I have a pipe system with an inlet flow of 400 m³/hr at around 2 bars

The output is just an outlet into the environment.

 

When I apply the boundary conditions I cannot map an inlet boundary condition with those two values.

I get negative pressures in the results.

 

pipe system:

11.PNG

Pressure results:

Capture.PNG

 

inlet flow settings:

inlet.PNG

openings:

openings.PNG

ambient settings:

ambient settings.PNGf

 

 

How do I model an inlet boundary condition with a volume flow AND a pressure and why do I get negative pressure on the way - even with the absolute display i get 0.1 Mpa max

 

Regards

 

Marco

2 REPLIES 2

Re: How to properly model the inlet boundary condition to get realistic pressure values

Gears Phenom Gears Phenom
Gears Phenom

You have to select only one of variables. Pressure rese and mass flow overpredict fluid flow. You can select or mass flow (rigid boundary condition) and inlet pressure will be estimated during analysis  or pressure rise (soft boundary condition) and you get mass flow as result.

Re: How to properly model the inlet boundary condition to get realistic pressure values

Solution Partner Experimenter Solution Partner Experimenter
Solution Partner Experimenter

The pressure outputted is a gage pressure, relative too your ambient pressure.

 

Also like previously mentionned specifying both the pressure and volume flow rate would over constrain the problem.