Wall shear stress in fluent is different than in cfd Post

I get different results in fluent and in cfd Post when i plot the contour of Wall shear stress (fluent) or the wall shear(cfd-post).

Comments

  • peteroznewmanpeteroznewman Member
    edited March 2018

    Please describe this in more detail.

  • helena_melhelena_mel Member
    edited March 2018

    I want to calculate the wall shear stress in fluent and plot the results in cfd post. In fluent postprocessing  I get the wall shear stress under wall flux and then I select wall shear stress and the surface and the contur plot is generated.

    When I opened the results in cfd post, there is wall shear too but when i plot the wall shear at the same surface i get different results. Is the wall shear stress in fluent the same as wall shear in cfd post?

     

  • Raef.KobeissiRaef.Kobeissi United KingdomMember
    edited March 2018

    Yes it is maybe the contour was different (contour map) and not the values. Can you send 2 photos for comparison please.

    cheers

  • shaheen wahabshaheen wahab BelgiumMember
    edited August 2018

     Hello Helena,

    How did you solve that problem of Wall shear stress? Does it come very small values as well? (e.g. order of -3)

    Thanks 

  • KremellaKremella Forum Coordinator
    edited August 2018

    Hello Shaheen, 

    Have to tried to use the same scales?

    Also, another important difference between Fluent and CFD post is the fact that CFD post displays node based results.

    Can you try and plot your contours in Fluent based on the node values? Please make sure you have this option checked.

    Thank you.

    Best Regards,

    Karthik

  • shaheen wahabshaheen wahab BelgiumMember
    edited September 2018

    Thank you so much, Karthik

  • JamaspJamasp Member
    edited July 3

    Hello Peter,

    I have the same issue with WSS. I did the following simulation with V17.0 and noticed that the WSS between Fluent and CFD post is different. Could you please explain the reason? The result is different for 10-6!! 

    I did new simulations with V19.2 and did not have this issue.

    Thanks,

    Jimmy

  • JamaspJamasp Member
    edited July 3

    Hello Kremella,

    Could you please address my question regarding the difference in WSS between Fluent and CFD post?

     

    Thanks,

    Jimmy

  • JamaspJamasp Member
    edited July 3

    Hello Raef,

    Could you please address my question regarding the difference in WSS between Fluent and CFD post?

     

    Thanks,

    Jimmy

  • kkanadekkanade Forum Coordinator
    edited July 6

    Can you please insert some zoomed in image. 

    As you mentioned, 19.2 is working, please use 19.2.

    17 is very old build. 19 might have some fixes. 

    Regards,

    Keyur

     

    If this helps, please mark this post as 'Is Solution' to help others.

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  • JamaspJamasp Member
    edited July 6

    Hello Keyur,

    Thank you so much for your reply. I would appreciate it if you or ANSYS team can provide a clear answer to this issue. Is it a bug in CFD post? Please check out the high quality images in the following. The simulations here are FSI and I'm just showing the results of the fluid domain. Notice that the simulations shown in v17 and v19 are two different problems with different boundary conditions. Do not compare the values of WSS. My concern is why WSS in CFD post is 10-6 smaller than Fluent??!! The WSS in CFD post is divided by 10e+6 for some reason. I'm opening the same case and data files in Fluent and CFD post but I'm getting two different values for WSS!!!

    Simulations in Ansys V17.0 showing at time step 2.36s.

    Wall shear stress in Fluent:

    Wall shear stress in CFD post, which is 10e-6 smaller than Fluent!! Why??!

     

    New simulations in v19 showing at time step 2.36 s.

    Wall shear stress in Fluent:

    Wall shear stress in CFD post, which matches the results in Fluent. 

     

     

    Best,

    Jimmy

  • kkanadekkanade Forum Coordinator
    edited July 7

    This is strange. 

    Can you please quickly check scale of the problem using scale provided at the bottom as shown in image below. Please check it in fluent and cfd-post. 

  • JamaspJamasp Member
    edited July 8

    Hello Keyur,

    I also added the ruler. It shows the same scale in Fluent and CFD-Post!! This is very strange!!! I'm opening the same cases in Fluent and CFD-post. Is it a bug in CFD-post? Or is it kind of non-dimensionalized values of WSS showing in CFD-post? As I mentioned, the WSS values in CFD-post are divided by 10e6. Could you please ask Ansys team to explain the reason for this difference between Fluent and CFD-post? Knowing the reason is very important for us.

    Results in Fluent

    CFD-post results

    Thanks,

    Jimmy

  • JamaspJamasp Member
    edited July 9

    Hello Keyur,

    Thank you for following up regarding this issue in CFD post. I would appreciate it if you find out the issue for us.

     

    Hello Peter,

    Could you also provide some information regarding this problem, please? It's very critical for us to know why this is happening.

     

    Thanks,

    Jimmy

  • kkanadekkanade Forum Coordinator
    edited July 10

    Can you please check in latest 2020R1. 

    Soon 2020R2 will be released. 

  • JamaspJamasp Member
    edited July 10

    I did the simulation that shows different results between Fluent and CFD-post in V17.0 but I opened the results in V19.2. I also opened the results in 2019R3 and got the same thing. We don't have 2020R1 on campus, unfortunately. Is the issue related to the version? It seems that CFD-post shows the WSS values in MPa but the unit in the legend shows Pa, instead. Any ideas?

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