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No Convergence CFD Analysis

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Old   September 17, 2018, 20:59
Default No Convergence CFD Analysis
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Hi everyone,
This is my first time using the Autodesk CFD software so I'm not sure if I'm doing the problem wrong or if its the software.

I created a 3D model on Inventor and tried an analysis. The model is the interior of a pipe (basically I modeled the fluid in the pipe, not the physical pipe itself) and put in an thin orifice piece in the middle. The model is 3 ft and 0.8 in long with a diameter of 0.3 in. The thin orifice pipe in the middle has a thickness of 0.8 in, with the orifice hole diameter as 0.03 in.

In the CFD analysis software I assigned 3 volumes (the two long volumes on either end of the orifice and the small volume through the orifice hole) as Skydrol Fluid (in compressible). The thin orifice piece was assigned as stainless steel 304.

I then put two boundary condition sets, an inlet temperature (72 F), pressure (3800 psi) and volume flow (5.2 GPM) and an outlet pressure (3200 psi).

Once I run the simulation I am not getting any convergence on the plot and I am pretty sure my temperature should be changing over the length of the pipe but it stays constant and if I add a mid-plane there are these small colorful patches across the length of the pipe.

Am I not using the software correctly or is my problem using bad data?

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Old   September 18, 2018, 10:22
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Jon Wilde
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Your model is over constrained.
Remove the pressure from the inlet

Check your Mach Number too, you might need to set this up as a compressible simulation...
Take a look in the help files, all you need should be there
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Old   October 3, 2018, 11:49
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Thank you!
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