Seeking guidance in how to do: Mesh Independence Studies

Jeeloong · March 4, 2015, 18:16

Dear Experts,

I am so confused with mesh independency studies.

According to some I should varies the mesh densities without considering the y+ really much when doing mesh independence and after I get a stable solution (No changes in variable), I then move on the change the mesh side near the BL to capture the details.

My question is should I make 5 cases with same y+ but different mesh densities, run it and test the dependency

Or

run different mesh densities without considering y+(varies for all cases)

I was acknowledged that the mesh independence studies is numerically means that the core flow does not change?

Let say I keep on discretise it but somehow the different y+ for each cases will affect the solution for monitoring point right?

Thanks

Regards
JL

fluid23 · March 6, 2015, 15:21

That choice really boils down to what your figures of merit are (i.e. what are you trying to learn?). If the variables that you are looking at during your convergence studyare driven by boundary layer mesh (like drag for example) then you definitely want to make y+ a part of that process. If you are looking at something like mass flow (or even lift in some cases) that is less dependent upon boundary layer mesh then you can probably get away with neglecting it.

The safe bet, and what I usually tend to do, is make succesivly finer mesh iterations that account for both simultaneously that way you know that each model in the convergence study is as appropraite as the others.

March 4, 2015, 18:16	Seeking guidance in how to do: Mesh Independence Studies	#1
Jeeloong Member Join Date: Jan 2015 Location: United Kingdom Posts: 53 Rep Power: 11	Dear Experts, I am so confused with mesh independency studies. According to some I should varies the mesh densities without considering the y+ really much when doing mesh independence and after I get a stable solution (No changes in variable), I then move on the change the mesh side near the BL to capture the details. My question is should I make 5 cases with same y+ but different mesh densities, run it and test the dependency Or run different mesh densities without considering y+(varies for all cases) I was acknowledged that the mesh independence studies is numerically means that the core flow does not change? Let say I keep on discretise it but somehow the different y+ for each cases will affect the solution for monitoring point right? Thanks Regards JL

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March 6, 2015, 15:21		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	That choice really boils down to what your figures of merit are (i.e. what are you trying to learn?). If the variables that you are looking at during your convergence studyare driven by boundary layer mesh (like drag for example) then you definitely want to make y+ a part of that process. If you are looking at something like mass flow (or even lift in some cases) that is less dependent upon boundary layer mesh then you can probably get away with neglecting it. The safe bet, and what I usually tend to do, is make succesivly finer mesh iterations that account for both simultaneously that way you know that each model in the convergence study is as appropraite as the others.