SimScale CAE Forum

Ahmed body simulation help


#1

Brand new newbie - if that is possible

I am trying to run the Ahmed body simulation. I figured out boundaries and have my BoundVolumeFace all correctly placed around the Ahmed body. When I try to run the simulation I get the following errors:
The following faces are missing a boundary condition assignment. If you choose to proceed, a no-slip wall boundary will be assumed for those faces: solid_0_face_3, solid_0_face_10, solid_0_face_16, more …
and
Missing material assignment for the following entities: BoundingVolume

I’m guessing the walls would be slip conditions since they outline the boundary and are not involved in the cfd around the Ahmed body- they are faces 0-5 . I thought I had the walls set at slip with wall 2 as inlet and 3 as outlet, but I’m still getting the same error code.

I read the tutorial, but for whatever reason I cannot find material assignment. It doesn’t help that the tutorial and the present screens are a bit different.

Any help accepted.


#2

Hi @treid,

Could you post the link to the project? That would allow us to better identify the issue.

Cheers.

Regards,
Barry


#3

tutorial hex-dominant parameters


#4

Hi @treid,

Material assignment is not needed for an incompressible simulation like yours. However, there is a problem where the mesh you are using (which I assume is from the old tutorial) is basically broken as you can see below with the absurd number of illegal cells.

image

What you need to do now is to re-mesh the geometry. The boundary conditions from the tutorial can still be used and followed. As for the part where the solver says “if you choose to proceed…” it just means you need to assign the BCs to all the faces in the simulation if not it would just be assumed as a no-slip wall, which is alright but not the best practice as you want total control over all aspects of the simulation.

Cheers.

Regards,
Barry


#5

Ok, I worked on the ahmed body without any luck. So instead of beating an apparently dead horse, I started a new project.

. I found the faces missing a boundary condition and can chase those down. My problem right now is the same for the newly imported model- it says I need a material assignment for Body 2, (spoiler), Body 1 (main body), and Component 1_Body1 (the post connecting Body 1 and 2). I cannot find anywhere to assign a material to these components. When I click on Materials it only gives me materials for the flow sim, not the body.
TLR


#6

Hi @treid, so its a little confusing at the moment, hopefully this will get easier in the future. When you select the domain, it suggests that for external flows, you select a mesh and not a geometry. This is because the solids that are represented is not the solid that repressents the fluid, and this simulation is only interested in the fluid, and therefore assigning a material to the body and spoilers would make no difference on the flow. Assign the mesh under domain and assign the material (air) to the mesh.

Best,
Darren


#7

Hi Darren.
That sounds logical. I’ll give it a try and get back to you
TLR