CFD Master Class Session1


#1

Hi,

I just finished the airfoil simulation. It successfully ran but the problem is that it took 2360 minutes :sweat_smile: Therefore, my core hours reached 82%:slightly_smiling_face:

Any suggestion? Why did it take so long?

Here is the link: https://www.simscale.com/projects/Eshqin/master_class_session_1_1/


#2

Hi @Eshqin,

That is because you have a mesh that contains 46 million nodes. Typically for a standard airfoil you would expect anywhere between 10,000 to 1 million nodes for optimal results, 46 million nodes is much too fine and while will produce very accurate results (considering everything else is correct), the deviation of results between say 1 million and 46 million nodes would be less than 3-5%, not to mention that it is very computationally expensive, hence your usage of majority of your core hours.

A good suggestion would be not mesh it so finely and perform a mesh convergence study where you start with a very coarse mesh and continually increase how fine the mesh is by about 1.5 times generally till you see a deviation of results that is less than say 1-2%.

Hope this helps!

Cheers.

Regards,
Barry

P.S please note these are rough node numbers and not a good indicator of an optimal mesh. Optimizing a mesh is tricky and requires a lot of time and effort. In fact it is one of the biggest areas of consideration in CFD on generating the ideal mesh that is acceptable, accurate while not too computationally expensive.


#3

Hi @Eshqin,

Specifically, the smallest leading edge cylinder refinement should be 0.03 instead of 0.3, therefore causing a huge volume to be refined at one of the highest levels. This has meant that a large mesh size has been generated.

Fixing this will mean that further simulations will be much more efficient.

kind regards,
Darren


#4

Yep, youโ€™re right @1318980 that is a big mistake I have made but actually, I really didnโ€™t think large mesh size like this will be generated.

Best wishes!


#5

Thanks, @Get_Barried for a well-explained reply. @1318980 informed me why tons of nodes had been generated. In refinement, radius of cylinder should be 0.03 instead of 0.3

Fail fast Learn fast!:slightly_smiling_face:

Best wishes!