Learning Forum

[Drew Logsdon]

Hello,

 

I am working on 2D simulation of a rectangular duct. My computation domain consists of a 1 inch tall by 20 inches long duct attached to an "open space" at the end to simulate free-stream conditions.

 

My goal is for a given inlet mach number to vary the back pressure of the "open space" so I can see the effect it has on the shock train formation in the rectangular duct section.

 

I am having trouble getting my residuals to converge and I was wondering if anyone has some feedback/ideas for getting this model to work correct.

 

Here are my Fluent setup parameters:

General:

Density-based solver

Steady state

 

Models:

Energy equation on

 

Materials:

Air, ideal gas, sutherland viscosity

 

Boundary codnitions:

Pressure inlet: Total pressure 304,000 Pa, static pressure 52,900 Pa, total temperature 500 K (corresponds to mach ~ 1.8)

 

Far field outlet: Static pressure want to vary from 1.5x to 3x inlet static pressure, mach number 1.65, static temperature 300 K

 

Reference values: compute from inlet

 

Standard initialization from inlet

 

1000 iterations

 

Attached is an image of my computational domain with the boundaries labeled for reference.

 

I would really appreciate any input on this, I can't seem to get my result to converge. Thank you

[Rob]

Don't use far field with a pressure inlet. Depending on the length of the exhaust jet you may need to extend the outlet region. Finally, with pressure in & out the massflow becomes part of the solution which makes the initial condition more important: you may need to patch the jet flow. 

[Federico Alzamora Previtali]

Hello Drew,

I would suggest that you place the pressure farfield boundaries much further from the outlet of your tube than what is shown in your figure. You want to minimize any interaction between the exiting flow and those farfield boundaries. 20X tube cross-section distance from the outlet would be a good start.

 

I hope this helps!