SimScale CAE Forum

Rear wing external aerodynamic simulation mesh problems


#1

I´ m having problem with the mesh of my simulation. I tried to create a mesh with prism layers but it appears that in some regions around the wings profile they were not created. I don´t know what parameters I need to change to correct this.

https://www.simscale.com/projects/math_marques96/rear_wing_mesh_study/


#2

@vgon_alves
@Get_Barried
@jousefm


#3

Hi Matheus!

We’re having a look at this as soon as possible!

Best,

Jousef


#4

Hi @math_marques96,

Your initial mesh setup and geometry look fine. Will need to play around with the meshing settings. Currently, the mesh in not usable due to the high number of illegal cells. Usually this indicates a poor geometry but you’ve adjusted the quality controls for layer generation. Will copy your project over and see what I can find out. May take awhile though.

Cheers.

Regards,
Barry

EDIT: Some update, translating the geometry to STL solved some of the issues, however the layers are not generating throughout the entire surface of the rear wings just only at some areas (about 70%). Still tuning it, but a good first step would be to translate the geometry to STL.


#5

Thank you very much,

I will make this change of the geometry to STL.

I realize that when I used a bigger level of surface and feature refinement and a bigger bounding box resolution, it helped in generating more layers around the wings, but did not cover the entire surface and the number of cells in the mesh grow to high, like to almost 13 millions cells (for just a wing simulation I expected to have a good mesh with much less cells).


#6

Hi @math_marques96,

13 Million cells is quite alot for such this relatively simple geometry. There is def alot of optimizing that needs to be done.

If we can hit layer generation of around 95% I think we can call it a success. So far that has been rather elusive. Am unsure at the moment if the issue lies with quality control deleting the layers or the layer generation not generating at all in the first place (i suspect the first).

We should continue to tinker with it and find a solution as this will be very useful for not only your simulations but for future use as well. Let me know if you manage to get the layers out. I will continue to tinker on my end.

Also could you share your calculations for the layer generation? What Y+ are you aiming for?

Cheers.

Regards,
Barry

EDIT: I also think a geometry adjustment is needed in that you need to round the end edges of the rear wing. Maybe give it a 0.1 round or something. Sharp edges typically cause the laying process to freak out. A 0.1 round will not adversely affect your simulation anyway.


#7

Hi @Get_Barried

I am aiming for a Y+ of 1. I used the flat-plate boundary layer theory for the height of the first cell mesh and after calculated the total height of the boundary layer using the aproximation that the boundary layer total height is 1.4*Y, Y been the blasius solution for a laminar boundary layer. After this I used a aspect ratio of 1.35 and find that I needed 14 layers. In the end I calculated the thickness of the final layer for the implementation in simscale, by using the total thickness , aspect ratio and number of layers.

Would be better to do this rounds at the Cad software?

Best Regards


#8

Hi @math_marques96,

I do think at this point as we are having meshing issues to use wall functions instead and keep your y+ between 30 and 300 (strictly between this range, no more or less) so that we can get some results out and see how close they are without needing to spend a long time getting the ideal layer generation out.

Reconsider this and if you’ve adjusted your settings for layering let me know. Also probably an expansion ratio of 1.35 is easier to work with and we may be able to get all the layers out after reconsideration of the y+, so keep using that if possible.

Yes you will need to add rounds in the CAD software. I tried adding rounds directly but no luck, the edge is too sharp. You will need to go back to the 2D outline, before extrusion, and round the end before extruding out. Do ensure that during assembly, there is no interference. Maintain the file as STEP and upload another as STL so we have some various formats to work with should one prove problematic.

Cheers.

Regards,
Barry


#9

Hello @Get_Barried

I made these changes and used a y+ of 30 and had to change some number of the mesh refinement. With it I could cover almost all the wing surface. But in when I looked the results of my simulation, almost all of the top part of my wing has a Y+ < 30. What could go wrong? Maybe I have to make the layers calculations to a number greater than 30 to ensure that all the wing surface will have a Y+>30?

I have a question about the boundary box layers. I will star to setup the simulation for the front wing, so the ground will have a great importance. I see that in a youtube FSAE video of SimScale it was used a boundary box layers in the floor. I do not understand why you have to use it, since the floor actually doesn´t have a boundary layer because it is “moving” in relatio to the car (is not a wall), and what is the calculations I need to do to have the parameters of it ( number of layer, first cell size, etc.).

Best regards