Insights about my simulation

Project Support
1

Hi,

As I have gone through post-processing and also some of your videos on youtube, I can not fully understand how the model is doing or how the car performs, so can you please give me some thoughts about the results and also the meshing? I have done many meshings and the best quality I can get is .40 is it any good? and what is your recommendation? Thank you

2

Hi there, and thanks for using the forum!

Some usual checks we do for quality of results are:

  • Residuals (under convergence plots): yours are all below 1e-3 at the last iterations, which is good:

image
image1534Ă—888 40.4 KB

  • Convergence of quantity of interest, in this case aerodynamic coefficients. In this case here I look at the last 30% of iterations and they look almost completely converged.

image
image1538Ă—882 21.5 KB

  • For the forces plot, it looks a little less ideal, with some values still oscillating. But I would say it is acceptable.

image
image1540Ă—887 31.7 KB

  • Finally for the y+ value, given that you used the default wall model and wall functions. It should lie between 3 and 300, and we have:

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image780Ă—664 48.6 KB

I would say that the results are good according to these criteria. You can in principle pursue for more precision, but it might not be worth the extra effort and cost. It is up to you and your needs.

3

Hi @moustafa_hamed,

Thanks for reaching out on the forums. I had a look at your project, and agree with the information Guillermo has provided. As he pointed out, the drag on your vehicle is not fully converged yet; there’s still a small downward slope:

Drag in Y direction
Drag in Y direction2560Ă—1352 143 KB

You will want to run the simulation until this flattens out; perhaps 500 more iterations.

I did notice 1 fairly large problem with your simulation setup: your Wheel definition via “Wall 6” and “Wall 7” boundary conditions do not have the correct “Point on axis.” This value needs to be the center of your wheel. You can see below tha the Point on axis is offset for the front wheel.

Wheel BC
Wheel BC2560Ă—1352 253 KB

Once you fix this in the setup, I recommend rerunning the analysis, and then doing a Mesh Sensitivity Study to determine if your results are mesh independent.

Thanks,
Matt

4

Thank you all for your replies i really appreciate it

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