# The dimensionless grid spacings

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 July 23, 2024, 11:05 The dimensionless grid spacings #1 New Member   chunlong Tan Join Date: Sep 2022 Posts: 8 Rep Power: 3 Dear all, I want to know how to solve Xplus, Yplus and Zplus in CFX-post. Thank you.

 July 23, 2024, 18:37 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,789 Rep Power: 143 Using your chosen expression for X+, Y+, Z+ define a variable with those expressions in CFD-Post. Note that Y+ probably already exists as a solution variable if you are doing a turbulent simulation - but read the documentation about it to make sure it is using the definition you want. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 July 23, 2024, 21:19 #3 New Member   chunlong Tan Join Date: Sep 2022 Posts: 8 Rep Power: 3 In these expressions, the height of the first layer grid on the wall needs to be used, but I don't know how to reference this variable

 July 23, 2024, 21:51 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,789 Rep Power: 143 The variable is called "Wall Distance" and will be produced when you use a turbulence model which requires it - that is SST and its related models. Wall distance is not required for turbulence models like k-e so it is not available with those models. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 July 23, 2024, 23:11 #5 New Member   chunlong Tan Join Date: Sep 2022 Posts: 8 Rep Power: 3 Thank you very much for your reply. I found this "Wall Distance" in my CFX-POST. But how do I get Δx,Δy,Δz?

 July 23, 2024, 23:14 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,789 Rep Power: 143 What is your definition of Dx, Dy and Dz? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 July 23, 2024, 23:49 #7 New Member   chunlong Tan Join Date: Sep 2022 Posts: 8 Rep Power: 3 I am currently using large eddy simulation for aerodynamic analysis of compressor blades. The relevant reference suggests paying attention to the x+,y+ and z+. According to relevant references, Δx, Δy, and Δz are the grid spacing of the spanwise, pitchwise, and streamwise in the cascade passage, respectively. （In my opinion, they are the grid spacing of three different directions）

 July 23, 2024, 23:55 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,789 Rep Power: 143 There is no easy way of getting these parameters as there is no easy way of defining the span, pitch and streamwise directions. If your geometry is aligned to the coordinate axes it is straight forward, but in general there is no easy way to get this. In the past when I did that sort of work I estimated it manually by looking at the mesh and measuring the distance between nodes in the appropriate directions. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

 July 24, 2024, 02:48 #9 New Member   chunlong Tan Join Date: Sep 2022 Posts: 8 Rep Power: 3 I get it, thank you again.