How to include inlet/initial fluctuations in PyFR to trigger the instability/turbulence

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Chandra Shekhar Pant

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Aug 25, 2020, 3:16:06 AM8/25/20
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Hi all,

I am trying to simulate a jet using the PyFR. To trigger the turbulence/instability I need to include the inlet/initial fluctuations in the velocity field. Is this easily doable, how to do that? Any suggestion and comment will help me a lot. Thanks in advance.


Giorgio Giangaspero

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Aug 25, 2020, 10:08:30 AM8/25/20
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Hi Chandra,

we will provide a patch relatively soon (say a month or two, I am doing the last test runs...) which will add synthetic turbulence generation capabilities to PyFR.
 In the meantime, if you are just interested in adding some fluctuations to the flow to trigger some instabilities, I would suggest using source terms, see [solver-source-terms] of the .ini file in the user guide.

Best
Giorgio

Chandra Shekhar Pant

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Aug 26, 2020, 2:47:53 AM8/26/20
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Hello Giorgio,

Thanks a lot Giorgio for your quick response and help. Really excited to see this functionality in the PyFR.
Is it possible to add something  like tanh(y) profile for the velocity at the inlet and in addition to that would the random white noise like srand() kind of function will work. Sorry for asking asking so many questions in a single thread.

Sincerely,
Chandra Shekhar Pant

Giorgio Giangaspero

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Aug 26, 2020, 3:29:25 AM8/26/20
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Hi Chandra

yes standard functions like tanh(y),sin,cos  work with boundary conditions and with source terms, the random function doesn't work. So I would use a combination of the above standard functions to have an inlet bc or source terms that is space and time dependent.

Best
Giorgio

Chandra Shekhar Pant

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Aug 27, 2020, 2:52:29 AM8/27/20
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Hello Giorgio,

Many thanks for your prompt reply and help. I will try to include your suggestions and will update you.
Thanks again for your time and help.

Sincerely,
Chandra Shekhar Pant
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