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a fully developed pipe flow in LES with mapped BC |
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April 12, 2020, 08:21 |
a fully developed pipe flow in LES with mapped BC
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#1 |
Member
bany
Join Date: Nov 2019
Posts: 50
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When i use the mapped BC to obtain a fully developed circular pipe flow in LES with pisoFoam, i get a false u profile along the radial direction which increases with time.
And in this case, my y+~5, and the offset is set to (0.025 0 0).The length of the pipe is 30mm and the initial velocity is (110 0 0). I set the setAverage to true to maintain the pipe flow. To ensure the Re being 10500, i set the nu=1.57e-5. Can anyone tell me why i cannot obtain a fully developed circular pipe flow with those setup. Any advice are appreciated! |
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May 25, 2020, 09:17 |
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#2 | |
Member
Guanjiang Chen
Join Date: Apr 2020
Location: Bristol, United Kingdom
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Quote:
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May 25, 2020, 18:45 |
the Additional file
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#3 | |
Member
bany
Join Date: Nov 2019
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Quote:
In addition, i try to use the wallfunctions. Unfortunately, i also cannot get a fully turbulent pipe flow. For more details, you can look up the attachments! All cases can be run by blockMesh ——> pisoFoam |
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May 26, 2020, 13:42 |
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#4 | |
Member
Guanjiang Chen
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Quote:
If I set, I will also set boundary layer like you. I don't know whether calculating for longer time can show turbulent pipe flow. Did do some Urans case and in Urans case is there turbulent flow? What I think can try maybe using cyclic boundary for inlet and outlet. Making nearwall mesh better is also a choice. Sincerely, Guanjiang |
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May 26, 2020, 21:14 |
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#5 | |
Member
bany
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Quote:
In addition, i have tried to use the cyclic BC with the gradp to force the flow. And by this method, we can get a fully turbulence. However, i do not know why i cannot get a fully turbulence by mapped BC or wallfuncions in LES. Whatever, thanks for your attention. |
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May 27, 2020, 05:20 |
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#6 | |
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Guanjiang Chen
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Location: Bristol, United Kingdom
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They shows different results. The mapped boundary condition is special I think. |
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May 27, 2020, 06:10 |
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#7 | |
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bany
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Thanks for your continuous answer! |
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May 27, 2020, 06:20 |
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#8 | |
Member
Guanjiang Chen
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Location: Bristol, United Kingdom
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May 27, 2020, 08:25 |
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#9 |
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bany
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May 28, 2020, 08:02 |
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#10 | |
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Hesam Tofighian
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What is your divScheme for velocity? Maybe the numerical diffusion damps eddies? Also, eddies formation stars from the boundary layer, so you need to resolve it. |
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May 28, 2020, 08:23 |
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#11 | |
Member
bany
Join Date: Nov 2019
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Quote:
You can see in the pipe-wallfunction where i set wall functions for nut and k in order to resolve the eddies near the wall. However, the wall functions seem to be invalid. By the way, the wall functions, i think, is fitted with the y+. In short, thanks a lot. |
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September 17, 2020, 08:28 |
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#12 |
New Member
Ran Yi
Join Date: May 2019
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Hi bany,
I just encounter the same problem with you: the "laminar" mean velocity profile after using mapped BC at the inlet. Have you found out the solution? BTW, besides mapping U, do you think it is necessary to map other parameters, such as nut and k...? Appreciate anyone who can give some advice on this issue. Thanks! |
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April 18, 2023, 15:25 |
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#13 | |
Senior Member
CFD_Lovers
Join Date: Mar 2015
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Quote:
Did you find out the reason? I am applying mapped B.C. on pipe flow for a LES simulation and the results inside the pipe does not look instantaneous to me. |
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May 25, 2023, 11:15 |
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#14 | |
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I am also working on a similar problem, maybe we can help each other. Do you apply the mapped BC to the U field only or also to nut and k? Thanks, J |
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May 25, 2023, 11:25 |
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#15 | |
Member
Guanjiang Chen
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I have abandoned the mapped BC. What I do is conducting the RANS simulation first and then set the RANS results as the initial set for the LES. Regards, Guanjiang |
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May 25, 2023, 11:37 |
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#16 |
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Hi Guanjiang,
Thanks for the prompt response. What boundary conditions do you then use in your LES if not using the mapped BC? |
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May 25, 2023, 11:41 |
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#17 | |
Member
Guanjiang Chen
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What I do is a basic problem of incompressible flow past a cylinder. I fixed the velocity at the inlet and fixed the pressure at the outlet. For the nut, I just use zeroGradient at the inlet and outlet. There are many boundary matches tutorial online. You can try and get a best one. Regards, Guanjiang |
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June 2, 2023, 21:31 |
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#18 | |
Member
bany
Join Date: Nov 2019
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Quote:
The fully developed turbulence in LES can be obtained by refinemesh in the wall regions. It is the only way where i got a fully developed turbulence with LES. However, the refined mesh near the wall will lead to more time cost. Any advice will be appreciated! |
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June 9, 2023, 08:53 |
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#19 | |
New Member
Join Date: Jun 2023
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I am now also working on LES for fully developed turbulent channel flow. However, even my y+ is controlled below 2, the velocity profile indicates that the flow might not be fully developed turbulent flow. If convenient, could you please tell me about your boundary conditions, the difference scheme for the convective term, and how many circulations have you run to get the fully developed turbulent flow? Thanks for your time, Regards, Junrui |
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June 9, 2023, 11:29 |
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#20 | |
Senior Member
CFD_Lovers
Join Date: Mar 2015
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Quote:
In addition to the mesh refinement adjacent to the wall, I suggest you to switch to cubic convective schemes in your fvSchemes dictionary. Using this, I could solve the problem of turbulence generation in my pipe flow case. Sina |
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