[Blanco]

Hi Xinguang,

I don't have experience with sonicFoam, but I think for sure you need to define mu and mut -> cinematic viscosity with varying density, laminar and turbulent, in order to perform your compressible simulation. In the results you will get the rho field and it will be used by yPlusRAS to calculate y+ values.

[JasonWang3]

Hi Andrea

As you said, yPlusRAS could give the yplus at the wall after I generate the rho fields. But the value is quite small than I expected, since I calculate yplus using the yplus calculator:
http://geolab.larc.nasa.gov/APPS/YPlus/
yPlusRAS give the value of 0.03 compare with 1 of the yplus calculator.

But in the website, there is no information about the calculation. So I think I should calculate the yplus by hand to compare with the results of OF.

Thanks for your reply.

[Blanco]

Hi Xinguang,

yes you can check at a wall what is the y+ value "by hand", but I'm pretty sure you will find that OF is using the right formula. Check my post #37

http://www.cfd-online.com/Forums/openfoam-solving/116358-how-calculate-y-plus-2.html#post530569

and check your wall boundary. The y+ formula in OF is exactly the one used in every calculator.

Best,

Andrea

[jaydeepKhajure]

Hello,

Currently I am running the case in OpenFOAM 2.3.0. I am having a problem calculating the y plus value. My case is in sonicfoam having Re 3e6 and I am using K-Epsilon RAS model. However, after post processing I type the command yPlusRAS in terminal, I get following error message,

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Create time

Create mesh for time = 0

Time = 0
Calculating wall distance

Writing wall distance to field y

Reading field U

Reading/calculating face flux field phi



--> FOAM FATAL IO ERROR:
cannot open file

file: /home/cae/OpenFOAM/cae-2.3.0/run/jaydeep/Pen_3D_4.5/constant/transportProperties at line 0.

From function regIOobject::readStream()
in file db/regIOobject/regIOobjectRead.C at line 87.

FOAM exiting

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Can anybody suggest a possible solution to overcome this error message ?

Thanks and Regards
jaydeep

[Blanco]

OF doesn't find the transportProperties file inside the correct path. Check if it's there, OF needs to check what RANS model you are using and what are the nu or mu values.

[JasonWang3]

Originally Posted by jaydeepKhajure

Hello,

Currently I am running the case in OpenFOAM 2.3.0. I am having a problem calculating the y plus value. My case is in sonicfoam having Re 3e6 and I am using K-Epsilon RAS model. However, after post processing I type the command yPlusRAS in terminal, I get following error message,

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Create time

Create mesh for time = 0

Time = 0
Calculating wall distance

Writing wall distance to field y

Reading field U

Reading/calculating face flux field phi



--> FOAM FATAL IO ERROR:
cannot open file

file: /home/cae/OpenFOAM/cae-2.3.0/run/jaydeep/Pen_3D_4.5/constant/transportProperties at line 0.

From function regIOobject::readStream()
in file db/regIOobject/regIOobjectRead.C at line 87.

FOAM exiting

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Can anybody suggest a possible solution to overcome this error message ?

Thanks and Regards
jaydeep

copy a transportProperties file to the constant folder

try yPlusRAS -compressible -time [time folder]

Before this, change the mut wall bc to mutLowReWallfunction, which is used to calculate the yPlus value.

[hamide]

hello friends
i'm new in openFoam. i want to calculate y-plus in openFoam. i don't know how!!!
it's turbulent duct flow with Re=3e+5
would you please help me?

[JasonWang3]

change wall bc in the mut file as mutLowReWallFunction, and in the terminal 'yPlusRAS (-compressible) (-time)'.

Hope it is helpful.

[hamide]

Originally Posted by JasonWang3

change wall bc in the mut file as mutLowReWallFunction, and in the terminal 'yPlusRAS (-compressible) (-time)'.

Hope it is helpful.

i don't have mut file!!!!
i have p,u,nut,k and epsilon File

[JasonWang3]

In the nut file, nutLowReWallFunction, then type in yPlusRAS

[Elham]

Hi,

I am doing simulaion inside a channel with Re=4900 based on channel half width. The channel is 10mm*60mm*10mm. The mesh is 50*300*50. The flow direction is in y-direction. I use yPlusLES utility but I get weird results. the yPlus in all over the domain, near or far from the wall, is very small, let's say maximum 3.
I also calculated
UPlus=U_mean/Utau
Utau=sqrt(gardP*h)
h=half channel width
I put gradp in respect to spanwise direction. I am not pretty sure that this gradP is correct. I got it by adding gradP in controlDict.

Thanks for any comment.

[Bashar]

Hi,
I am little confused! So, I am running an LES simulation flow past plate with Re=50000. If I use the yPlusLES will this give me ystar or yplus? I am using pimpleFoam.Also if I want to comput the y+ around the plate and not the full domain , how can I do that?


Sent from my iPhone using CFD Online Forum mobile app

[Bashar]

Thanks , I found the answer.
In my version , 3.0.1, I used yPlus command to get it.
Thanks a lot.

[crazzy.pirate43]

Hi everybody,

So now, How can I calculate y+ without any SGS model in LES? as I have no nuEff

[piu58]

Originally Posted by crazzy.pirate43

Hi everybody,

So now, How can I calculate y+ without any SGS model in LES? as I have no nuEff

You only need the wall shear stress for that. Calculate the wall forces, and analyse the shear stress over your surface. With that you may get your y+ coordinate by



You get the friction velocity using the wall shear stress.


With this calculated for a point you may express the y-value of the first cell center. This is the y+ values the tools in OF give.

[crazzy.pirate43]

Dear Uwe,
thanks a lot for the quick reply. I think I managed to get it by put turbulenceProperties file as a laminar in the studied case after the run and just put the utility command yPlus

Thanks

[LThomes]

Hello everyone,
I'm simulating the flow past a sphere using k-omega SST model and I'm trying to calculate the yPlus on the sphere. I tried to type "yPlusRAS" in the terminal, as you said, but it gives me the following message:

[ofuser@default c9]$ yPlusRAS
bash: yPlusRAS: command not found

I'm using OpenFOAM v1612+ for Windows.
Can anybody help me?

[LThomes]

Originally Posted by LThomes

Hello everyone,
I'm simulating the flow past a sphere using k-omega SST model and I'm trying to calculate the yPlus on the sphere. I tried to type "yPlusRAS" in the terminal, as you said, but it gives me the following message:

[ofuser@default c9]$ yPlusRAS
bash: yPlusRAS: command not found

I'm using OpenFOAM v1612+ for Windows.
Can anybody help me?

In my OpenFOAM version I have to type pimpleFoam -postProcess -func yPlus

[kooki_13]

hi
I am doing open channel for simulating atmospheric boundary layer with openFoam. my solver is pimple and the LES model is oneEqEddy. and I do not know how can I calculate y+. domain size is 1400,1000,100 m and thats whye the first y+ became so large!

[RobertHB]

Originally Posted by kooki_13

and I do not know how can I calculate y+.

Take a look at post #55.
You can get the wall shear stress by using the wallShearStress postProcessing functionality and calculating its magnitude. Remember that OpenFOAM uses kinematic pressure and that you have to multiply your wallShearStress by the density of your fluid.

For your mesh size, try to use mesh grading or snappyHexMesh to refine the section of your mesh close to the wall.