How to apply Neumann Boundary Conditions in Star-CCM+

sophiasteward · October 2, 2019, 23:40

As mentioned in the title, I'm trying to apply Neumann BC or derivative BC to a STAR-CCM simulation and not really finding much on the internet. The simulation is air flowing through a tube.

Thanks!!

cwl · October 3, 2019, 03:04

You mean - to set up a derivative on the boundary? - Like this:

For which variable?

lzw · October 3, 2019, 20:04

It looks like the flux?

cwl · October 3, 2019, 20:09

Quote:

Originally Posted by lzw

It looks like the flux?

Exactly. Just wanted to clarify - "flux" of what.

sophiasteward · October 10, 2019, 17:38

Velocity. It was suggested to me but I'm not sure if I entirely understand what I'm doing yet. Currently simulating air flow in a large tube 1.5 m dia tube with atmospheric pressure at the inlet and outlet.

cwl · October 10, 2019, 17:46

Something is missing in your task description: you cannot have zero pressure drop while having the flow of air in the pipe, unless it's an inviscid approach.

sophiasteward · October 10, 2019, 17:50

I have an inlet velocity of 20 m/s, so the momentum of the air is carrying it through the tube.

cwl · October 10, 2019, 17:53

Quote:

Originally Posted by sophiasteward

I have an inlet velocity of 20 m/s

Then you can just set the velocity inlet boundary condition (± extrusion for boundary layer development depending on the task) at inlet and pressure outlet on another side.

Where does Neumann BC come from?

October 2, 2019, 23:40	How to apply Neumann Boundary Conditions in Star-CCM+	#1
sophiasteward New Member Sophia Join Date: Oct 2019 Posts: 3 Rep Power: 6	As mentioned in the title, I'm trying to apply Neumann BC or derivative BC to a STAR-CCM simulation and not really finding much on the internet. The simulation is air flowing through a tube. Thanks!!

October 3, 2019, 20:04		#3
lzw New Member Zhengwei Long Join Date: Oct 2019 Location: Tianjin, China Posts: 8 Rep Power: 6	It looks like the flux? cwl likes this.

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October 3, 2019, 03:04		#2
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 436 Rep Power: 17	You mean - to set up a derivative on the boundary? - Like this: For which variable?

October 10, 2019, 17:38		#5
sophiasteward New Member Sophia Join Date: Oct 2019 Posts: 3 Rep Power: 6	Velocity. It was suggested to me but I'm not sure if I entirely understand what I'm doing yet. Currently simulating air flow in a large tube 1.5 m dia tube with atmospheric pressure at the inlet and outlet.

October 10, 2019, 17:46		#6
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 436 Rep Power: 17	Something is missing in your task description: you cannot have zero pressure drop while having the flow of air in the pipe, unless it's an inviscid approach.

October 10, 2019, 17:50		#7
sophiasteward New Member Sophia Join Date: Oct 2019 Posts: 3 Rep Power: 6	I have an inlet velocity of 20 m/s, so the momentum of the air is carrying it through the tube.