## [CFD] Calculating Initial Conditions for Turbulence

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Snail With a Shotgun
Snail With a Shotgun
0
Joined: Fri Jul 08, 2022 8:42 pm

### Re: [CFD] Calculating Initial Conditions for Turbulence

Thanks a lot Vyssion, I've been running quite a few simulations lately and your explanation was very helpful .

That said, something doesn't feel quite right and I think turbulent intensity might be to blame. A friend of mine told me to use turbulent intensity of 0.1%, which seems too low to me (AFAIK even the most advanced wind tunnels can only go as low as 0.5% (?)). Could you please shed some light on what values one might want to use for automotive use and when to use them?

Vyssion
Moderator / Writer
Joined: Sun Jun 10, 2012 1:40 pm

### Re: [CFD] Calculating Initial Conditions for Turbulence

Snail With a Shotgun wrote:
Fri Aug 12, 2022 6:06 pm
Thanks a lot Vyssion, I've been running quite a few simulations lately and your explanation was very helpful .

That said, something doesn't feel quite right and I think turbulent intensity might be to blame. A friend of mine told me to use turbulent intensity of 0.1%, which seems too low to me (AFAIK even the most advanced wind tunnels can only go as low as 0.5% (?)). Could you please shed some light on what values one might want to use for automotive use and when to use them?
Sounds like your friend is having issues with convergence, and has "hacked" it by just switching turbulence so close to "off" it doesn't matter

Your numbers aren't too far off. Default for most CFD is usually set at 5%. Depending on what it is you're analyzing, that can sometimes be a little high, and you might want to opt for say 2-3% as a standard. 1% would be quite low turbulence, but wind tunnels can get down to 0.5% yes, and even below that too.

What exactly "doesn't feel right" in your simulation?
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