yPlusLES: compressible flow
 

Hi All ,

I am new to openFOAM. I just finished a compressible LES with OpenFOAM. When I want to use yPlusLES to calculate the y+ in my case, I got the messege to provide nuSGS. I think this quantity is only for incompressible flows. Could anyone know how to calculate the y+ in compressible flows?

Thank you so much!

Hi openfoammaofnepo,

I managed to remember two details:

1. The yPlusLES and yPlusRAS should both have the "-compressible" option, but I've taken a look into it and only the yPlusRAS has got one. You can check by running:
   
   Code:

   ---

   yPlusRAS -help

   ---

2. This problem isn't new. You can calculate yPlusLES in a compressible simulation, by using a function object, while the solver is running. For more information about this and the report about the missing feature: http://www.openfoam.org/mantisbt/view.php?id=802

Best regards,
Bruno

Thank you wyldckat!

I am using OF211, but this problem has been fixed in OF210 maybe.

Hi openfoammaofnepo,

I forgot to mention the version... In OpenFOAM 2.2.0 you can use yPlusLES as a function object in a compressible simulation, as indicated here: http://www.openfoam.org/version2.2.0...processing.php - this link is shown in the other link in the previous posts.

As for yPlusLES application itself, it has not yet been fixed to use compressible, not even in OpenFOAM 2.2.x, which is the very latest bug fix version of OpenFOAM.

Best regards,
Bruno

Thank you wyldckat.

If I would like to calculate yPlus for compressible LES using OF211, how can I do it? Could you please give me some hints?

thanks.

Hi openfoammaofnepo,

I've made a note to look into this next week.

In the mean time, have a look into the source code of the "yPlusLES" application in your own OpenFOAM version. You can find it by running this command:
Then compare with the source code on OpenFOAM 2.2, namely this file: https://github.com/OpenFOAM/OpenFOAM...LES/yPlusLES.C - compare the methods "calcIncompressibleYPlus" with "calcCompressibleYPlus", with the ones on the application you've got.

As to modifying an OpenFOAM application, check this tutorial: http://openfoamwiki.net/index.php/Ho...ure_to_icoFoam

Best regards,
Bruno

Hi openfoammaofnepo,

Done! I've created the "yPlusLESWCompressible" utility for OpenFOAM 2.2.x and then back-ported to 2.1.x. Simply follow the instructions given here https://github.com/wyldckat/yPlusLES...swcompressible

Hopefully everything will work as intended. At least the tests I've made seemed to indicate that everything was OK.

Best regards,
Bruno

Can not get some post processing
 

Good afternoon,

I tried to get the y+ or the wall shear stress, in order to put some probes for some tests, but unsuccessfully.
The simulation I did, was compressible LES, and the OpenFOAM version I am using is the 2.0.1 (maybe where the problem is).
I tried to compute y+ with the command yPlusLES but it gave me this error:

I saw the previous posts, and typed for the compressible case, but it said it was an invalid option. And I also saw the code, and seeing that the transport properties is used for incompressible, I think my version does not have the possibility to compute y+ for compressible flow in this way.

Is it possible to get what I need, without running the simulation again ? And if so, will I need the function object ?

(Doing an upgrade in my version will be complicated.)

Greetings guilha,

Try following the latest instructions given here: https://github.com/wyldckat/yPlusLES...ble/tree/of210

Best regards,
Bruno

Hi Bruno,

Thank you very much for your help.

When I compiled it using wmake yPlusLESWCompressible, I got the following information:

make: *** No rule to make target `yPlusLESWCompressible'. Stop.

Do I need to add something in the Make folder? Thank you very much.

http://www.cfd-online.com/Forums/ope...tml#post376918

Zou can also have a look at this thread.

Hi wyldckat,

Sorry to bother you. Could you please give me some suggestions about how to compile the yPlusLESWCompressible package? When I compiled it I had the problem I mentioned in the last thread. I am not very familiar with C++ compilation. Thank you and happy new year!

Greetings to all!

@owayz: :eek: I had no idea someone else had already provided a compressible y+ for LES!

@openfoammaofnepo:
I need to know:

1. The exact instructions you have followed to try and install "yPlusLESWCompressible".
2. Which exact version of OpenFOAM are you using and how you installed it.
3. Which Linux Distribution are you using.
4. What is the complete output that you get. That last error message is far from enough to figure out what's wrong :(.

Best regards,
Bruno

Hi,

1, The install procedure is from the following:

https://github.com/wyldckat/yPlusLES...swcompressible

I put the install package in the folder:
/users/openfoammaofnepo/OpenFOAM/openfoammaofnepo-2.1.1/utilities/yPlusLESWCompressible-of21x/yPlusLESWCompressible

2, The OF version is 2.1.1
3, the Linux version is Distributor ID: ScientificSL
Description: Scientific Linux SL release 5.5 (Boron)
Release: 5.5
4, The complete output info is (after inputting the command wmake yPlusLESWCompressible)
make: *** No rule to make target `yPlusLESWCompressible'. Stop.

Thank you very much.

Hi openfoammaofnepo,

:eek: OK OK, got it. You did not perfectly follow the instructions written on the page ;)
Whoops... and I forgot to write the command for unzipping it :( That explains why you didn't perfectly follow the instructions :( Sorry about that.

OK, the exact instructions should be:
The detail here is that you are running the wmake command from within the folder "yPlusLESWCompressible" and not from its parent folder. This is why you get that error message.

You have two possible solutions:

1. While you are still within the folder "yPlusLESWCompressible-of21x/yPlusLESWCompressible", simply run:
   
   Code:

   ---

   wmake

   ---

2. Or while you are still within the folder "yPlusLESWCompressible-of21x/yPlusLESWCompressible", go back to the parent folder and build as originally described. In other words, run:
   
   Code:

   ---

   cd ..
wmake yPlusLESWCompressible

   ---

Best regards,
Bruno

Hi wyldckat, successfully installed. Thanks.

Hi wyldckat,

When we run wmake in the folder yPlusLESWCompressible-of21x/yPlusLESWCompressible, which file or executable is run for this command? Thank you very much.

Hi openfoammaofnepo,
I'm not sure I understand your question, because the "obvious" answer would be: it's wmake, it's a script that will take care of building the application on demand. You can find more information about this in the User Guide: http://www.openfoam.org/docs/user/co...plications.php

Best regards,
Bruno

Dear Bruno,

When I run yPlusLESWCompressible -compressible, I found that there is an error information about my thermodynamics option:

The version of OF is 2.1.1, and I think the thermodyanmic library should be fine for my case. But I am not sure why this error comes from. Do you have the problem when you use it? Thank you so much.

Hi openfoammaofnepo,

I need more specific information on how you have configured the "thermodynamicProperties" file and how you load your customized thermodynamics library.

Best regards,
Bruno

Hi wyldckat,

Thank you very much for your help. For example, in the following tutorial:

Then after I run XiFoam, and then will get some results. If I apply this utilities for the time director 0.0002

I got the following output:

But of course, for the two cases you provided in the package, the utility is fine. Thank you very much.

Hi openfoammaofnepo,

Thanks for the detailed description! It a lot easier to reproduce the same error!

I've updated the branch "of21x" on the repository. Follow the download and installation instructions once again from the updated page: https://github.com/wyldckat/yPlusLES...ble/tree/of21x

The new utility is named "yPlusLESWCompressibleNCombustion", so try it instead of the utility "yPlusLESWCompressible".

Best regards,
Bruno

Thank you so much, Bruno.

That can be used now. But it is specific for the thermophysical options. Thank you.

Dear wyldckat,

Thank you so much for your help.

In the utilities you upload recently:

yPlusLESWCompressibleNCombustion

In the following source files:

I think when we calculate the yPlusLES for combustion, we need to use the following one:

Here I think the rho is needed to get the correct values. Please give me some comments if there is any problems.

Thank you so much.

Hi openfoammaofnepo,

You might be correct. I honestly only handled the procedure of "replace 6mm screw" for a "8mm screw"... I didn't check if things were all held together properly, since I didn't know how exactly to ascertain if it was correct or not. Although the "yPlus" field is non-dimensional as a result, so I assume that everything is working as intended.

So my question is: what is the reasoning you've followed for making that suggestion?
In addition: are you using the "-compressible" option for running the application?

Best regards,
Bruno

Hello,

Thanks.

I just followed the definition of yPlus like

Without the rho, yPlus is not dimensionless, although the values obtained from it will show no big difference.

I use the option '-compressible' and it is OK.

Thank you for your sharing.

Hi openfoammaofnepo,

OK, let's see how I can manage LaTeX equations here on the forum... based on these wiki pages:

• http://www.cfd-online.com/Wiki/Dimen...e_%28y_plus%29
• http://www.cfd-online.com/Wiki/Friction_velocity
• http://www.cfd-online.com/Wiki/Wall_shear_stress

The fully extended equation is:

In contrast, the equation present on the utility is this (if I'm not mistaken):

:) Yes, you are correct!!! It's missing a inside the square root! Feel free to report this at the official bug tracker: http://www.openfoam.org/bugs/ - since this problem is present in the original code of the function object "yPlusLES".

If you don't want to report this yourself, I can report this for you.

Best regards,
Bruno

Dear Bruno,

Thank you for your help. What do you mean by "original code"? We do not have the original compressible LES yPlus. In the incompressible version, the equation should be correct.

If it is convenient for you, please help us to report this to them. I think we need to correct. Although the values of yPlus will not have big difference, however, conceptually it is not correct without rho. Thank you for your help.

Best,
op**po

Hi openfoammaofnepo,

It's available as a function object, as explained here http://www.openfoam.org/version2.2.0...processing.php - and I quote:
The original code is located at "src/postProcessing/functionObjects/utilities/yPlusLES": https://github.com/OpenFOAM/OpenFOAM...LES/yPlusLES.C

OK, I'll report this in a minute and edit this post indicating the bug report.
edit: Reported here: http://www.openfoam.org/mantisbt/view.php?id=1141 - I'll wait for them to fix the issue and then I'll propagate the fix to my repository.

Best regards,
Bruno

OK, many thanks!

I always use OF211 and so I did not find that. Thank you for your help!

Have a nice Sunday!

Besides, just for curiosity, how did you input the equations in the thread? ......simple questions for you.

There is a forum here at CFD-Online for help regarding using the forum itself: http://www.cfd-online.com/Forums/sit...k-discussions/
There you'll find this thread: http://www.cfd-online.com/Forums/sit...ne-forums.html

Got it, many thanks!!

Hello Bruno,

Any update from the bug report? Was it indeed a bug or just any other saying? Just for my knowledge. Thank you so much.

Hi openfoammaofnepo,

You can see for yourself ;): http://www.openfoam.org/mantisbt/view.php?id=1141 :rolleyes:

Best regards,
Bruno

Hi openfoammaofnepo,

I've done some more homework and prepared 2 test cases that solve pretty much the same simulation, but using compressible vs incompressible variants of the same solver, namely pimpleFoam vs rhoPimpleFoam. The cases are provided in the bug report and also in my repository.

The conclusion is that I do believe that you are right in affirming that "rho" is missing inside the square root and these two test cases seem to prove that. Therefore, I've applied this fix to the source code in the utilities at my repository.

Best regards,
Bruno

Thank you for your information, Bruno!

Have a nice day!

Well, the bug fix has finally been implemented in 2.2.x: http://www.openfoam.org/mantisbt/view.php?id=1141

The commit can be viewed here: https://github.com/OpenFOAM/OpenFOAM...17f4ec1bde1348

The strange detail is that Henry chose to implemented the division by "rho" in both occurrences of "mu", instead of using the single multiplication by "rho" inside the square root.
There are two possibilities for this:

1. By dividing by "rho" in both parts of the equation, it might be numerically more stable than using the simplified equation.
   • It makes sense, because the flow near the wall should be small enough and on a similar scale of "mu/rho". This would minimize the loss of numerical precision during the math operation.
2. Or he simply couldn't spend any time thinking more about this.
   • Given his first quick comment/reply on this bug report, leading to him to close it and not accepting it as a bug report, it's a possibility.

If tomorrow I can remember to get around to this, I'll implement the same bug fix on my repository.

Thank you, Bruno. I read their updated code of yPlusLES. At least from the the point of view of math, it is correct. I cannot say more in terms of numerical precision. Do they provide any awards for the bug reports? :-) :-)

In my case, certainly not :) I've been a pain sometimes with my bug reports :rolleyes:.

But usually the award is the feeling we get that when we feel that we're helping something we like to get even better.