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pimpleFoam vs simpleFoam vs pisoFoam vs icoFoam?

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Old   April 3, 2013, 16:07
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... so it is (should be) based on the Reynolds number of the flow.
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Old   April 4, 2013, 02:35
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There is no real reason to use icoFoam, consider it deprecated. All the other solvers should support turbulenceModel laminar, so even for low Reynolds numbers you can use those instead.
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Old   May 17, 2013, 12:08
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I used both pimpleFoam and icoFoam to solve the flow around circular cylinder at Re=100 in 2D.

According to my simulations icoFoam gives better results in terms of Str number, which is 0.164 but in pimpleFoam it is 0.144. Both Foam gives the same good drag coefficients.

for future research I need to much higher Re simulations so icoFoam can not be used. But according to the poor performance of pimpleFoam at Re=100, I'm not sure at higher Re pimpleFoam would yield accurate result.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
later I found out that I added relaxatin factor, which is the very cause for loosing accuracy in strouhal number , in pimpleFoam, Since I deleted the relaxation part good results are now obtained.

Last edited by kkpal; May 18, 2013 at 04:28.
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Old   January 7, 2014, 04:41
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Hi kkpal,

Thanks for your info, it really a good point. However, if I use icoFOAM for high Reynolds number, but with the turbulence off, i.e. DNS, do you think I'll get the same results if I use pimpleFoam with the same setting.

Thanks.
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Old   January 7, 2014, 05:54
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Quote:
Originally Posted by mali View Post
Thanks for your info, it really a good point. However, if I use icoFOAM for high Reynolds number, but with the turbulence off, i.e. DNS, do you think I'll get the same results if I use pimpleFoam with the same setting.
Yes, that should give you the same results.
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Old   January 17, 2014, 12:46
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Hi Julien,

I saw your post and just want to ask whether icoFoam is able for turbulent flow or not?

In terms of DNS, both laminar and turbulent flow solve the same equation, given that I have very fine mesh and reasonable Reynolds number, can I get turbulent flow?

Thanks and regards,
Tony
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Old   January 27, 2014, 23:35
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Hi Tony,

As mentioned by Bernhard, you should able to get the turbulent flow if the Reynolds number is in the turbulent region.
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Old   January 28, 2014, 06:13
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Hi mali,

Thank you very much for replying. I am trying that but I just wonder whether anyone succeeded before since I don't want to spent so much time on something unrealistic.

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Tony
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Old   January 29, 2014, 16:53
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Hi,


if it is possible to use icoFoam for a turbulent flow (DNS, fine mesh, turbulence off, high Re-number) does this mean I can investigate transition flow from laminar to turbulent as well?

Which strategy is the best to investigate transient flow, for the case that I start with a laminar flow regime (Re~200) that changes to turbulent flow due to an applied heat flow, and finally the resulting turbulent flow?

without heat transfer
LES: icoFoam + filtering + Subgrid-Scale model
or
DNS: icoFoam (very fine mesh)

with heat transfer
LES: buoyantBoussinesqPimpleFoam + filtering + Subgrid-Scale model
or
DNS: buoyantBoussinesqPimpleFoam (very fine mesh)

?


Aylalisa

Last edited by aylalisa; January 30, 2014 at 06:15.
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Old   June 13, 2014, 09:20
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Quote:
Originally Posted by aylalisa View Post
Hi,


if it is possible to use icoFoam for a turbulent flow (DNS, fine mesh, turbulence off, high Re-number) does this mean I can investigate transition flow from laminar to turbulent as well?

Which strategy is the best to investigate transient flow, for the case that I start with a laminar flow regime (Re~200) that changes to turbulent flow due to an applied heat flow, and finally the resulting turbulent flow?

without heat transfer
LES: icoFoam + filtering + Subgrid-Scale model
or
DNS: icoFoam (very fine mesh)

with heat transfer
LES: buoyantBoussinesqPimpleFoam + filtering + Subgrid-Scale model
or
DNS: buoyantBoussinesqPimpleFoam (very fine mesh)

?


Aylalisa
for DNS w/o heat transfer, I use pimpleFoam, because it can add source term with fvoption. For DNS with heat transfer, I use buoyantPimpleFoam, because the density in my case is variable.
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Old   August 4, 2015, 05:07
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Hello everyone,

at the moment I am working with pimpleFoam, too. I have an airfoil in a channel with turbulent flow. Here I use the pimple Algorihm as Simple with relaxation Factors, adjustTimeStep no and Co > 1 (implizit).
Might anyone of you explain me the connection between adjusttimestep and the relaxation factors? When do I use both togehter oder just one of it. At the moment I am a little bit confused about it.

The next step is an oszillating velocity, so the case became transient. Do I have to change the pimple Algorithm tp piso or can I leave it in simple?

Thank you for any reply

best regards,
Stephie
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Old   August 5, 2015, 20:14
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Quote:
Originally Posted by stephie View Post
Hello everyone,

at the moment I am working with pimpleFoam, too. I have an airfoil in a channel with turbulent flow. Here I use the pimple Algorihm as Simple with relaxation Factors, adjustTimeStep no and Co > 1 (implizit).
Might anyone of you explain me the connection between adjusttimestep and the relaxation factors? When do I use both togehter oder just one of it. At the moment I am a little bit confused about it.

The next step is an oszillating velocity, so the case became transient. Do I have to change the pimple Algorithm tp piso or can I leave it in simple?

Thank you for any reply

best regards,
Stephie
Hi Stephie,
adjustTimeStep switch could be used to adjust the time step size by the solver, if you want to limit the CFL number below some specific value. The solver will decrease the time step size if the CFL number is higher than a specified value.
Relaxation factors help in convergence, so if you have can achieve convergence of the problem the relaxation factors don't make much difference. If the solution diverges you can try lowering the relaxation factors.
Relaxation factors and adjustTimestep don't have any connection. You can use both of them if you want for their intended purposes.
Yes in case of transient simulation you will have to use pimple or piso algorithm. The simple algorithm can only used for steady or quasi - steady simulations.
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Old   August 18, 2015, 06:16
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Hey,

thank you for your answer. It was very helpful.
I know it was still discussed, but I am really confused about the pimple alogrithm. Might you explain it again?
I know pimple is a combination of simple and piso. For using piso I need a CO<1, by simple it can be higher.
When i want to implement pimple as simple wich number of nCoorectors and nOuterCorrectors do I have to use?
I read http://openfoamwiki.net/index.php/Op...hm_in_OpenFOAM, but for me it isn't easy to understand.
I thought for simple the number of nOuterCorrectors have to be > 1. But when I read the text, I understand the nCorrector is important and this number should be over 1.
It would be very nice if you might explain it again.

Thank you so much and best regards,
Stephie
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