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Author Topic: Pyrosim issue  (Read 3649 times)

jonas

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Pyrosim issue
« on: April 26, 2017, 07:49:36 am »

Pyrosim has this warning when i want to export to FDS, how can i solve it?
Warning:
a reaction (&REAC) must be defined in order to simulate burning in FDS. This model currently includes objects that require a reaction, but no reaction has been specified
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Jon Albrecht

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Re: Pyrosim issue
« Reply #1 on: April 26, 2017, 08:24:03 am »

Jonas,

The good news is that you can safely ignore that warning. I'll also give you the history of that warning as I understand it, to make you sure you know how it pertains to you.

In FDS5, if a user didn't specify a &REAC record but the model included a combustion reaction (specified by a burner surface or some other means), a default reaction was assumed. I believe this default was propane. In the transition from FDS5 -> FDS6, this default reaction was removed by the team at NIST. Their belief, as I understand it, is that users were using the default reaction out of convenience, even though it was only appropriate for a very limited subset of fire simulations.

In order to try and simplify the user experience, we experimented with different default reactions in PyroSim over the years. Eventually we decided that we aren't experts on modeling of fires, and decided to remove our default reaction support.

When this change occurred, we decided it was appropriate to warn users if no reaction was specified as they ran their models. If you are not trying to simulate a combustion reaction, or you've specified a reaction elsewhere, you can safely click 'Ignore' and proceed with your simulation.

If you need more guidance on reactions in FDS / PyroSim, it may be worth spending some time reading through the FDS User's Guide. Also feel free to browse our tutorials, located here: http://www.thunderheadeng.com/pyrosim/tutorials/

Regards,

Jon
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jonas

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Re: Pyrosim issue
« Reply #2 on: April 26, 2017, 09:48:41 am »

Jon,

Thanks. but i have another error when i run fds...
the photo is my issue, fds discover a error about the mesh...
how can i solve it? thanks.

Jonas
Jonas,

The good news is that you can safely ignore that warning. I'll also give you the history of that warning as I understand it, to make you sure you know how it pertains to you.

In FDS5, if a user didn't specify a &REAC record but the model included a combustion reaction (specified by a burner surface or some other means), a default reaction was assumed. I believe this default was propane. In the transition from FDS5 -> FDS6, this default reaction was removed by the team at NIST. Their belief, as I understand it, is that users were using the default reaction out of convenience, even though it was only appropriate for a very limited subset of fire simulations.

In order to try and simplify the user experience, we experimented with different default reactions in PyroSim over the years. Eventually we decided that we aren't experts on modeling of fires, and decided to remove our default reaction support.

When this change occurred, we decided it was appropriate to warn users if no reaction was specified as they ran their models. If you are not trying to simulate a combustion reaction, or you've specified a reaction elsewhere, you can safely click 'Ignore' and proceed with your simulation.

If you need more guidance on reactions in FDS / PyroSim, it may be worth spending some time reading through the FDS User's Guide. Also feel free to browse our tutorials, located here: http://www.thunderheadeng.com/pyrosim/tutorials/

Regards,

Jon
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Jared

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Re: Pyrosim issue
« Reply #3 on: April 26, 2017, 10:40:56 pm »

This error is referring to a vent improperly setup within Mesh 1.  So the issue is with the vent, not the mesh.  Ensure that your vent is on the plane of the mesh that you created and this error should be solved.
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jonas

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Re: Pyrosim issue
« Reply #4 on: April 27, 2017, 10:24:35 am »

Thanks a lot Jared.
I solve it but have another issue was discovered.....
how can i solve it?..
Sorry.
This error is referring to a vent improperly setup within Mesh 1.  So the issue is with the vent, not the mesh.  Ensure that your vent is on the plane of the mesh that you created and this error should be solved.
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Jared

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Re: Pyrosim issue
« Reply #5 on: April 28, 2017, 08:17:15 pm »

Add a &REAC line to your model.  Look at the user manual and search for &REAC.  Currently you are telling the model that "X" is going to burn but you aren't saying what the properties of the burn will be.  That is what the &REAC line will do.
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