Learning Forum

[Zou_]

Hi everyone, nI'm currently working on an academic project on Ansys about a turbulent flow in a canal and i want to plot Uplus vs Yplus.nI created some custom functions in order to plot that but the plot seems off even though the other results (friction coefficient, wall shear stress) are right.ncan anyone help me ? thank you in advancen

[Karthik Remella]

Hello,nCould you please share with us the definitions of your U+ in CFF? Also, you are obtaining the y+ values directly from Fluent, right?nWhich Turbulence model are you using?nAlso, I've moved this question to the Fluids sub-category for better alignment.nThank you.nKarthikn

[Zou_]

Hello, nThank you for your response,nI am using SST K-Omega model nFor U+ , i made a custom function to define as U/U-tau nfor Y+ I've tried both using a custom function (Y+ = Y*U-tau/viscosity) and Yplus wall directly from FluentnI just started using Fluent so i'm not exactly surenI want to obtain a plot similar to this one nn

[Karthik Remella]

Hi, nWhat does your final plot look like? You need to have a good mesh resolution to capture this plot. Please see this HW problem in our Ansys Innovation Courses (AICs).nCan you please check this example to see if your set-up is overall correct?nThank you.nKarthikn

[Zou_]

Hi,nthank you for the tutorial, i followed all the steps mentioned in the video nThese are the plots i'm getting.nUplus vs Yplus is still off. nThe expressions i'm using are shown in the images belownCould u please give me the steps to plot it correctly ? nthank you in advance nn

[Karthik Remella]

Hello,nThe solution is dependent on your grid. It is important to have a good resolution near the wall. Please resolve the mesh near the wall carefully. You can study the mesh on the case I shared with you as a starting point. nThanks.nKarthikn

[Zou_]

Thank you for your response ,ni think my mesh is good enough to capture all the zones (as shown in picture, y+ on the wall is less than 5)ni think the custom fuctions i'm using are wrong nwould you please give me instructions about the functions to use in order to plot Uplus vs Yplus nn

[Amine Ben Hadj Ali]

Ansys Fluent Theory Guide does cleary mention how uplus and yplus are formulated. By the way almost all solver do not use classic uplus but instead ustar which is built with TKE to avoid getting singular values on stagnation regions.nnOther point: having yplus below 5 is nice but is not sufficient if you are not properly resolving the BL with at least 10-15 cells across it.n