Steady>Compressible>Laminar flow

mba_olufemi · August 31, 2018, 10:14

Hi,
I am not entirely sure this is the right place to ask my question, but since it is related to the boundary conditions maybe someone could help.
I am trying to setup a simulation of air flowing inside of a pipe (tube) using HELYX-OS. I followed the nice slides of Mr Combest found here. http://download2.nust.na/pub4/source...2013_Jeju/Tue/Track2-3_DanielCombest.tar
The example provided ran without problems. It simulates water running in a pipe of diameter 0.1 m and 2.5 m in length as Steady>Incompressible>Laminar flow.
Now, I am trying to modify the case model using the same mesh (I repeat, just a cylinder with an input patch, an output patch and a tube no-slip fixed wall) to Steady>Compressible>Laminar flow for air at the speed of 80 m/s. Eventually, if successful, I will modify the geometry fron cylinder to cone, which is what I really need.
But the problem I have is that it does not run at all. If I choose the same settings like on the example (input velocity “Fixed Value = 80” , input pressure “Zero Gradient”; outlet velocity Zero Gradient and Pressure “Fixed Value = 0” ) then HELYX-OS selects rhoSimpleFoam as the solver but it exits with the error:
Foam: :error: : printStack(Foam: :0stream&) at ??:?
I have experimented with different settings but always get an error.
Could someone please help?
Thanks a lot.
Mba

Robin.Kamenicky · September 2, 2018, 06:24

Hi mba,

I do not have any experience with HELYX-OS but you might want to change the outlet pressure. If you use 0 you will get a floating point error. If you want to resemble 0 Pa value use small pressure such as 0.001Pa.

Also the zeroGradient velocity at the outlet can make a problem, when the flow is not fully developed.

Let me know whether it works.

Kind regards,
Robin

August 31, 2018, 10:14	Steady>Compressible>Laminar flow	#1
mba_olufemi New Member mba olufemi Join Date: Aug 2018 Posts: 6 Rep Power: 8	Hi, I am not entirely sure this is the right place to ask my question, but since it is related to the boundary conditions maybe someone could help. I am trying to setup a simulation of air flowing inside of a pipe (tube) using HELYX-OS. I followed the nice slides of Mr Combest found here. http://download2.nust.na/pub4/source...2013_Jeju/Tue/Track2-3_DanielCombest.tar The example provided ran without problems. It simulates water running in a pipe of diameter 0.1 m and 2.5 m in length as Steady>Incompressible>Laminar flow. Now, I am trying to modify the case model using the same mesh (I repeat, just a cylinder with an input patch, an output patch and a tube no-slip fixed wall) to Steady>Compressible>Laminar flow for air at the speed of 80 m/s. Eventually, if successful, I will modify the geometry fron cylinder to cone, which is what I really need. But the problem I have is that it does not run at all. If I choose the same settings like on the example (input velocity “Fixed Value = 80” , input pressure “Zero Gradient”; outlet velocity Zero Gradient and Pressure “Fixed Value = 0” ) then HELYX-OS selects rhoSimpleFoam as the solver but it exits with the error: Foam: :error: : printStack(Foam: :0stream&) at ??:? I have experimented with different settings but always get an error. Could someone please help? Thanks a lot. Mba

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September 2, 2018, 06:24		#2
Robin.Kamenicky Member Robin Kamenicky Join Date: Mar 2016 Posts: 74 Rep Power: 12	Hi mba, I do not have any experience with HELYX-OS but you might want to change the outlet pressure. If you use 0 you will get a floating point error. If you want to resemble 0 Pa value use small pressure such as 0.001Pa. Also the zeroGradient velocity at the outlet can make a problem, when the flow is not fully developed. Let me know whether it works. Kind regards, Robin