|
[Sponsors] |
April 7, 2017, 11:01 |
inflation and y+
|
#1 |
Member
kaouachi anouar
Join Date: Jul 2016
Posts: 66
Rep Power: 9 |
hello. please im very new in cfd and i need your help for calculation the both partamatres
1 firest layer height 2 maximum layer best regads |
|
April 8, 2017, 13:08 |
|
#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,674
Rep Power: 65 |
First you need to pick a desired y+. This is usually something like 1,2,5, 30, 100, etc.
Is it external flow or internal flow? If external, check out the following tools: https://www.cfd-online.com/Tools/yplus.php https://geolab.larc.nasa.gov/APPS/YPlus/ For internal, y+=1 is around 1% of the duct radius. |
|
April 8, 2017, 14:56 |
|
#3 |
Member
kaouachi anouar
Join Date: Jul 2016
Posts: 66
Rep Power: 9 |
hello thank you LuckyTran for you reply. son im woking for stepped spilways so its externel flow but i dont understant whish value i need for y+
my qustion is how i can know my y+ second how i can used inflation ? which value i need in first layer? height and maximum layer? and groth rate ? best regards |
|
April 8, 2017, 22:07 |
|
#4 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,674
Rep Power: 65 |
Honestly just mesh whatever and get a simulation going. After you have gotten a result, see if it makes sense. Don't be afraid to do the wrong thing and miss out on learning in the process.
You can't. You only know what the y+ is after you have solved the problem. All you can do is take an educated guess. That is, you hope that your 1st cell layer height ends up at approximately a certain y+ value. The desired y+ depends on your modelling approach. I.e. laminar or turbulent. If turbulent then what turbulence model you are using and then what wall treatment you want to use. You want to choose an approach grid size that is consistent with the model that you employ. But really, it is a user choice. You can pick anything, but your result may and probably will affected. Any number between 1 and 1.5 is reasonable for the growth rate. Small numbers gives more dense grids (which some people like for certain reasons) and large numbers gives fewer cells (which many people like). It's up to you. But unless you have a specific reason to want to change the growth rate, maybe you can just leave it alone. |
|
April 9, 2017, 06:20 |
|
#5 |
Member
kaouachi anouar
Join Date: Jul 2016
Posts: 66
Rep Power: 9 |
so i used k-eps RNG and standar wall traitement so whats value of + should be in my results ?
is my results of y+ wrrong whats the solution best regards |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
[ANSYS Meshing] Problems with creating a hex-uniform MultiZone Mash with Inflation | AnnaF | ANSYS Meshing & Geometry | 4 | April 19, 2019 06:24 |
[ANSYS Meshing] Inflation Layers Being Finicky | Markua | ANSYS Meshing & Geometry | 12 | April 28, 2015 07:11 |
Fluent diverges when using inflation layers | ziggo | FLUENT | 4 | August 9, 2013 12:11 |
Large Valve Flow Analysis - Inflation Problem | sercan85 | ANSYS Meshing & Geometry | 2 | June 1, 2010 14:02 |
Inflation | Gab | CFX | 6 | August 24, 2005 22:45 |