SimScale CAE Forum

Weird Numbers for forces and moments

Greetings

I was simulating incompressible flow for some f1 in schools car models with the same settings however the sixth model which i simulated racked in some weird numbers for pressure forces which were too big in comparison with other numbers that the other model racked in( for example the first model had a pressure force on the z axis of -0.452 whilst this model had a pressure force on the z axis of 62.49 on the latest iteration). I checked my mesh and the numerics,the boundary conditions they were exactly the same.So i need your help in figuring out my mistake.

Here is the link for the project: https://www.simscale.com/projects/ccharalambous/f1_in_schools-edge/

Kind Regards and thanks in advance,

Charalambos

Hi Charalambos!

First of all your domain is way too small to create useful results. Also the mesh settings can be refined adding some layers to it. Let’s see what our @CFD-SQUAD has to add here.

Best,

Jousef

Thanks for the advice .As for the mesh i know its quite coarse however i need to update to a better plan in order to have the capacity to mesh better

Hi @ccharalambous

@jousefm sir is absolutely correct regarding the domain size, you should increase the size of your domain. Simulating with this domain will give you meaningless results. Also, I can see that total number of faces with wall B.C. are different in the first(729 faces) and last simulation(723 faces), any specific reason?

Thanks
Ani

Hey,

The difference in faces is probably due to changes that i made to the design. About the faces for the first model with wall there were 735 and for the second 729.

Kind Regards,

Charalambos

Hi @ccharalambous !

I agree with @jousefm & @anirudh2821998’s observations. As a topological example for wind turbines you could do the following.

1.- You could resolved in a computational domain representing the surface boundary layer (SBL) with a length of 30D in the axial direction, 25D downstream and 5D upstream of the object. You can considerer width of the domain is 7D and the height is 5D.
2.- The D value is a characteristic length, I think you could consider a D equal to the width of the object.
3.-Also, I think that in your boundary conditions you could consider the following: inlet & oulet (OK), bottom (wall), right and left walls (empty), top (atmosphere).

Best !

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@ccharalambous: For external CFD simulation I would expect that you put your ‘Material Point’ outside your geometry. Currently it is inside ‘solid_7_face_5’.

Cheers,

Retsam

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Hi @Retsam sir

I remember @ccharalambous has already set external meshing option in the hex automatic mesh settings so according to me, there is no issue with the material point.

Thanks
Ani

Greetings

Thank you all for your suggestions and for the time you took to help me!

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