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Precision problems in Fortran in KIVA4

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Old   December 4, 2017, 10:24
Default Precision problems in Fortran in KIVA4
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zdz
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I use CHEMKIN DVODE to integrate the chemistry in KIVA, where the species concentrations are used as the inputs into DVODE. These species concentrations (Vay) are calculated by
Vay(: ) = spd(i4c, : )*rmw(: )
And this way to integrate the chemistry works fine. When I manipulate this to (this manipulation is due to an algorithm)
Vay(: ) = spd(i4c, : )*rmw(: )*vol(i4c)
Vay(: ) = Vay(: )/vol(i4c)

And the in-cylinder pressures and temperatures show huge error compared with the results before the manipulation.
I doubt that the small values of vol(i4c) is the source of the error.

I used gfortran compiler. Can anyone tell me how to avoid this kind of error in Fortran?
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Old   December 5, 2017, 07:39
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Ravindra Shende
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You are right. small values of 'vol' could be the source of the errors.
Using the governing equations in non-dimensionalised form could help. Or you can use quad precision (available with intel fortran compiler, not sure about gfortran).
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