[gush]

Hi,
it is adviced that y+ values should be around 1 when enhanced wall treatment is selected.

We can check that value from “adapt” section. But it is the max value!! Minimum and average values can be checked from Reports.

So my questions are
1-which value should we take into consideration? Max, min or average?

2-if min is very low( for example 1e-04) does this effect the simulation?

Thanks!!

[litzj]

if y+ value is very small, it affects badly for your convergence of your simulation

min and max value range should be chosen based on your tur. model

[AlexanderZ]

If you are using wall treatment than y+ should be significantly larger than 1,
for standard wall treatment it is around 30-50, for enhanced 50-200

Once you have made y+ ~ 1 you do not need wall treatment at all, switch it off

Best regards

[gush]

Originally Posted by AlexanderZ

If you are using wall treatment than y+ should be significantly larger than 1,
for standard wall treatment it is around 30-50, for enhanced 50-200

Once you have made y+ ~ 1 you do not need wall treatment at all, switch it off

Best regards

??

it is clearly discussed in user manual and in the forum that y+ needs to be equal to 1 for EWT.

now you say 50-200?!?

[LuckyTran]

AlexanderZ is confusing wall treatment for wall functions.

Some user judgment is required. It's entirely up to you. There is no laws regarding how to do CFD. My harsh response is to recommend you to wikipedia to better understand statistics: https://en.wikipedia.org/wiki/Statistics

But a more useful response...

Originally Posted by gush

So my questions are
1-which value should we take into consideration? Max, min or average?

2-if min is very low( for example 1e-04) does this effect the simulation?

Thanks!!

1 - Each are important to somebody. Max is the high-level check to make sure your mesh under a threshold. If the max is <1 then you are 100% sure your y+ is less than 1 everywhere. This is a good place to start.

Obviously you can have an average of 0.5 or 0.1 even with a max of 1. So the avg gives a better sense of what the typical quality is. Some people (myself included) also like to have a high min y+ in order to maintain suitably low cell count. Usually this is more of an optimization problem to minimize computational cost. Really what do you want your mesh to look like? At the end of the day it is your mesh and your CFD and not someone else's.

2 It is unlikely you can get a y+ that small for practical flows. If you did achieve such a low y+, it's not necessarily a problem. However, it's probably a hint that your solution is a bad one (because it's really hard to get such a small y+). Usually the problem is to get a small enough y+, why complain if it's small? At some point you need to stop being paranoid and just hit the damn run button, get some results, and learn something.