|
[Sponsors] |
June 24, 2020, 13:31 |
Calculating dx+ and/or dz+
|
#1 |
New Member
Mike
Join Date: Jul 2019
Posts: 5
Rep Power: 6 |
Good afternoon,
I am running various scale-adaptive simulations as part of a university research project. Naturally, such simulations entail a good deal of post/pre processing. I have found most of the germane quantities (such as y+, integral length scale, and SGS viscosity) relatively straightforward to post/pre process, either directly or with CFFs. With this said, I have yet to find a way to calculate dx+/dz+ in Fluent. Does anyone know of a way these can be calculated (using CFFs or otherwise)? While I am fairly certain my grid spacing is adequate, I would like to show some contours of the grid in terms of viscous units. I found only one other thread with a similar topic (dx+ and dz+). However, I think there was some confusion. Any help is greatly appreciated! |
|
June 24, 2020, 14:25 |
dx+ and dz+
|
#2 |
Senior Member
|
It will be straightforward to calculate and provided the mesh is structured. Otherwise, you need to find a way to define streamwise and transverse dimensions of the cells. This is not easy for unstructured meshes.
__________________
Regards, Vinerm PM to be used if and only if you do not want something to be shared publicly. PM is considered to be of the least priority. |
|
June 24, 2020, 15:08 |
dx+ and dz+
|
#3 |
New Member
Mike
Join Date: Jul 2019
Posts: 5
Rep Power: 6 |
Thanks for your reply, vinerm.
Unfortunately my geometry is not conducive to structured meshing. I assumed it would require a good bit of work to calculate, given my meshes are unstructured tetra. I just wanted to make sure I was not overlooking something in Fluent. As a side note for anyone else interested, in ANSYS "Quick Guide to Setting up LES-type Simulations" the authors claim dx+/dz+ can be approximated using the CFF "sqrt(face-area-magnitude)*y-plus/cellwall-distance." I suspect this is only accurate to within an order of magnitude though. Last edited by Leibniz; June 24, 2020 at 15:09. Reason: side note |
|
August 5, 2020, 00:44 |
dx+ and dz+
|
#4 |
New Member
Mike
Join Date: Jul 2019
Posts: 5
Rep Power: 6 |
Thought I would follow-up by saying this: the CFF I posted above provides a fairly good approximation. I wrote the necessary code to calculate the viscous grid (for my particular case) and found the above CFF to be within 25% of the calculated values. The approximation provided by the CFF degrades as skewness increases.
|
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Questions on dynamicTopoFvMesh | danvica | OpenFOAM Running, Solving & CFD | 80 | April 16, 2019 16:58 |
Long output in terminal. | ssa_cfd | OpenFOAM Running, Solving & CFD | 1 | March 18, 2019 05:25 |
DPMFoam - Serious Error --particle-laden flow in simple geometric config | benz25 | OpenFOAM Running, Solving & CFD | 27 | December 19, 2017 20:47 |
Problems in calculating the fluid traction on the current structure frame in 3D models | fw407 | OpenFOAM Running, Solving & CFD | 0 | August 6, 2008 12:04 |
How to update polyPatchbs localPoints | liu | OpenFOAM Running, Solving & CFD | 6 | December 30, 2005 17:27 |