SimScale CAE Forum

Geometry and Mesh problems


#1

Dear Forum,

I am working on a project where my friend designed a new car and he wants to know the drag of the car. But apperently the geometry is not ok, because mesh cannot be made due to (machine run out of memory). Could you please look at the geometry and suggest what should be done next?

Link: https://www.simscale.com/workbench/?pid=5143465712630531803&mi=spec%3Acc0f8d07-c356-40b2-b617-8950ca113fab%2Cservice%3AMESHING%2Cstrategy%3A9&sh=1

Have a nice day


#2

Hi @Zaapex!

That’s because your mesh settings are set too fine in order to work on your problem - as stated in the message you would need a higher number of cores. Try performing a mesh convergences study using 16 cores trying a relatively coarse settings first and then work your way up until you receive the message or the results are satisfying enough.

Best,

Jousef


#3

Hi @Zaapex Your simulation’s mesh event log is showing two error warning which are as follows.

1)The tesselated surface is not closed. There could be a problem with the CAD geometry (such as self-intersections). Please inspect your geometry. Trying to proceed anyway.

2)The machine ran out of memory. Please choose a larger machine by increasing the number of computing cores or reduce the fineness of your mesh.

The second error can be resolved as suggested by @jousefm (thanks for the advice).

But as far as the first one error is concerned, i suggest you to check your CAD model , make sure that the CAD model is clean.


Here, see that geometry event log is also indicating the issue with CAD model.
Also upload the STEP CAD format of the model inspite of PRC. STEP CAD format is less likely to create meshing problem.

Regards


#4

Thank you for your help. I successfully made a mesh which has some illegal cells, but I will try to solve that.


#5

I have changed the geometry and now the mesh looks ok with 18 bad cells. But my simulation starts to divergence (Rocketman_Sim - Run1) especially variables Uy and p. Can you look closer what was is wrong?


#6

Hi @Zaapex,
Recently checked out your simulation and find the following issues.
1)Try manually sewing all the sheet bodies together in CAD software. It can help with mesh issues.


2)Increase the maximum runtime for the job.

You can increase the maximum runtime here.
fsdfssd

Regards,
.


#7

What do you think about divergence in my project? I tried to improve the geometry and I do not think this is the cause. Maybe some boundary conditions are wrong or something else?

Longer runtime will not solve the issue probably.


#8

HI @Zaapex,
I will copy your project and I will share results soon. :upside_down_face:
by the way, it is tesla model S …?:thinking:
best,
Rohit.


#9

It is a modified version of it


#10

@Zaapex,

Maybe give that cool project a try here: https://unpluggedperformance.com/aerodynamic-study-of-tesla-model-3/?fbclid=IwAR3q_EzUNI3_9txdpt65koYXMdb8of_YQpRinZ47XuhL7w8qPahiH33FtOU :slight_smile:

Cheers!

Jousef


#11

hi @Zaapex
are you excited to see the results of CFD…?
this project takes almost 24+ hours to complete with 780 core hours. :astonished:
but the results were so satisfying for me beacuse cut plot look realistic. ( velocity across car)


but there was some strange thing was happen in pressure distribution plot.

I checked convergence plot & set up but there was not any mistake. I was run the project with Potential foam initialization was ON (i think this was a reason for this but not 100% sure.)
here is project link.
https://www.simscale.com/workbench/?pid=7181831327239740344&mi=spec%3A80cbc0ab-4208-49c7-abc2-16730c261672%2Cservice%3ASIMULATION%2Cstrategy%3A3&ps=analysis%2FIncompressible--oneOf%2FsimulationControl

best,
Rohit.


#13

In my case Potential Foram initialization was also ON, but I will just try with longer run time


#14

YES @Zaapex, its always ON by defaults. but in this case there were some strange behaviours was identify so in that case normally people try to run project with disabling the Potential Foram initialization.


#15

hi @Zaapex,
In addition, I also found out the Cd and lift on this tesla model.
Cd=1.7 but normally it was 0.24 with the stable condition (wheel not rotating ) but in this project, you added MRF for front and rear wheel. (but this rotating wheel can increase Cd from 0.24 to 1.7 ? )
normally the rotating wheel and other think increased the value of Cd but particularly I don’t know how much. so, its too hard for me to say that CFD Cd was right.
you have any data to validated CFD results?

cheers,
Rohit.


#16

I have also uploaded a CAD version and mesh of Tesla 3. Can you also simulate this?

With my simulation I get strange results. Forces are ok, but when you look at pressure field or velocity nothing makes sense


#17

HI @Zaapex,

Do you change anything in the CAD file?

yes…work in progress (55% completed)

share the project link with me.

best,
Rohit.