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Which Pressure BC Compatible with Advective Velocity BC?

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Old   March 2, 2018, 08:09
Default Which Pressure BC Compatible with Advective Velocity BC?
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Canakkale Dardanelspor
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Hi,

I use advective boundary condition for velocity outlet in an incompressible large eddy simulation. I confused myself for which type of boundary condition I must use to ensure outflow pressure condition is compatible with the advective velocity condition? Currently, the pressure condition is fixedValue.

Kind regards

PS: A similar question seems to be asked here.
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Old   March 4, 2018, 06:00
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Quote:
Originally Posted by HakikiCanakkaleli View Post
Hi,

I use advective boundary condition for velocity outlet in an incompressible large eddy simulation. I confused myself for which type of boundary condition I must use to ensure outflow pressure condition is compatible with the advective velocity condition? Currently, the pressure condition is fixedValue.

Kind regards

PS: A similar question seems to be asked here.
Hi,

I use the same combinaion and I think it's typical.

Regards,
Syavash
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Old   March 4, 2018, 07:43
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Hi,

I think this pairing can numerically be viable; however, in physical sense, seems incorrect to me. Because, for a spatiotemporally variant velocity field at the outlet, we force gauge pressure to zero, which shouldn't be the case as we let the velocity field out as is by using advective BC. I would prefer to use zeroGradient pressure, yet this is not possible for incompressible applications.

Thanks for your reply,
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Old   March 4, 2018, 08:01
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Quote:
Originally Posted by HakikiCanakkaleli View Post
Hi,

I think this pairing can numerically be viable; however, in physical sense, seems incorrect to me. Because, for a spatiotemporally variant velocity field at the outlet, we force gauge pressure to zero, which shouldn't be the case as we let the velocity field out as is by using advective BC. I would prefer to use zeroGradient pressure, yet this is not possible for incompressible applications.

Thanks for your reply,
You're welcome. I see your point and I suppose it is true either in case of zeroGradient for velocity at the outlet (instead of advective). However, I have seen a case of boundary-layer simulation which has used zeroGradient for pressure at the outlet. I can provide the link if you wish, but I remember the top boundary was specified as fixedValue for pressure which seems correct to me.

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Syavash
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Old   March 4, 2018, 09:21
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I would be glad if you could provide me the link, if possible.

Kind regards,
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Old   March 4, 2018, 09:35
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Quote:
Originally Posted by HakikiCanakkaleli View Post
I would be glad if you could provide me the link, if possible.

Kind regards,
Sure. This is the link, please let me know if you had any specific opinion after reading it.

https://www.google.ca/url?q=https://...hd2FHcoKcvUlrw

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Syavash
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Old   November 21, 2019, 00:01
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I am also using advective BC for velocity and fixedValue for pressure, is it the correct group of settings?
I have found that there is an increase in velocity around the outlet, but I have no idea about it.
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