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Solver problem with a big amount of reactions

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Old   April 6, 2007, 10:30
Default Solver problem with a big amount of reactions
  #1
Leonid
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My reacting mixture include more than 100 chemical reactions, but as I noticed Solver doesn't run when I add more than 72 reactions. Here is error message I get -

Error detected by routine POKECA CDANAM = CVAR CVALUE = EDMRATE_RC101_FL1 CRESLT = ADRS

ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | Stopped in routine MEMERR | ----------+

Is there any way to add more reations?

Thanks
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Old   April 6, 2007, 13:51
Default Re: Solver problem with a big amount of reactions
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opaque
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Dear Leonid,

What version of ANSYS CFX are you using? 5.7.1, 10.0 or 11.0?

Please report the issue with your help representative.

There are no hard limit on the number of reactions allowed; therefore, something must have gone wrong..

Opaque.

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Old   April 9, 2007, 11:38
Default Re: Solver problem with a big amount of reactions
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Bak_Flow
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Opaque,

how many reactions has the solver actually been tested on? I remember some time ago there were some limits!

Leonid,

are you actually serious about applying such detailed finite rate chemistry in CFX? You realize that solving transport equations for each species is not only going to be very computationally expensive (I don't know how much because you do not specify how many species are involved in the 72-100 reactions) BUT guess that it is 30+???

Not only does your computation effor increase because of the additional transport equations BUT as you move from a model with major species and reduced reactions TO a model with minor species and elementary reactions -> you drastically expand the time (and spacial...people often forget about this!!!) scales that need to be resolved! This means you probably cannot run with as big of time steps either! And it may not even run on the same mesh as a global reaction model!

Ok then the big one....is this a turbulent system. The detailed reaction mechanisms are only valid for homogenous systems so the mean sources (for species equations and energy) are not the same as the source evaluated at the mean values! All RANS will give you is the mean state values!

So all this effort may not give you anything useful anyhow?

Have you considered using a pdf based method? Do you have access in Ansys now to generate tables? Can CFX read PrePdf formats?

Things to think about....Bak_Flow

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