# Case configuration: start up, ini and mesh

**URL:** <https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239>\
**Category:** Just Starting\
**Created:** [4 June 2019 13:25 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239 "2019-06-04T13:25:13Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Douglas\_Fontes](https://avatars.discourse-cdn.com/v4/letter/d/51bf81/32.png) [@Douglas\_Fontes](https://pyfr.discourse.group/u/Douglas_Fontes)\
**Post date:** [4 June 2019 13:25 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239/1 "2019-06-04T13:25:13Z")

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Dears,

I am trying to use PyFR as a tool for my research. However, I am having some difficulties to obtain simple results in a 2D backward-facing step flow case. I have tried to run this case considering incompressible and compressible flow. However, even I reduce the Courant number (reducing the time step or the inlet velocity), I am obtaining NAN residues.

Please, could you configure this setup (backStep.ini and backStep.msh are attached) and give some feedback about the mistakes I am committing?

Thank you in advance,

Best regards,

[stepBack.zip](https://pyfr.discourse.group/uploads/short-url/3uS8wwyY3rLBsMVROLiJQAVP3G5.zip) (431 KB)

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**Author:** ![fdw](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@fdw](https://pyfr.discourse.group/u/fdw)\
**Post date:** [4 June 2019 17:28 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239/2 "2019-06-04T17:28:30Z")

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Hi Douglas,

So at a zeroth order I see that there are a couple of lines where

p = 0

which is clearly unphysical for it is specifying a null pressure.

Regards, Freddie.

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**Author:** ![Douglas\_Fontes](https://avatars.discourse-cdn.com/v4/letter/d/51bf81/32.png) [@Douglas\_Fontes](https://pyfr.discourse.group/u/Douglas_Fontes)\
**Post date:** [4 June 2019 18:18 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239/3 "2019-06-04T18:18:08Z")

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I understand. Could you send me a configuration (Incompressible or compressible) for this geometry, so that it can be executed on PyFR?

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**Author:** ![fdw](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@fdw](https://pyfr.discourse.group/u/fdw)\
**Post date:** [4 June 2019 19:26 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239/4 "2019-06-04T19:26:23Z")

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Hi Douglas,

I have not personally run this case and so do not have a geometry or  
input deck for it. Maybe someone else on the mailing list does, however.

Regards, Freddie.

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**Author:** ![Douglas\_Fontes](https://avatars.discourse-cdn.com/v4/letter/d/51bf81/32.png) [@Douglas\_Fontes](https://pyfr.discourse.group/u/Douglas_Fontes)\
**Post date:** [4 June 2019 19:45 UTC](https://pyfr.discourse.group/t/case-configuration-start-up-ini-and-mesh/239/5 "2019-06-04T19:45:46Z")

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I am providing the .ini and .msh files for this case. Could anyone help me to configure this case (flow inside a back-facing step, incompressible or compressible flow)?

Thanks

[stepBack.zip](https://pyfr.discourse.group/uploads/short-url/3uS8wwyY3rLBsMVROLiJQAVP3G5.zip) (431 KB)