how to convert to dimensionless scalar in openfoam
I'm already trying to write a code for simulating conformational rheological problems.
my code is complied well but when I try to use it this error appears:
--> FOAM FATAL ERROR:
Argument of trancendental function not dimensionless
From function trans(const dimensionSet&)
in file dimensionSet/dimensionSet.C at line 480.
I found the source of error may exist in these lines of my code:
//size of shear rate tensor (which is dimensioned scalar)
volScalarField sizegamadot = Foam::sqrt ( 0.5 * (twoD && twoD) );
//ci is a non-dimensioned variable which is calculated by this
//formula : ci = ((-0.0076*ln(sizegamadot) + 0.0385)/0.1876)^1.998
volScalarField ci = Foam::pow( ((-0.0076 * Foam::log (sizegamadot)) + 0.0385) / 0.1876 ) ,1.998 );
// solving equation for a.
== keisi * ( (twoD & a_) + (a_ & twoD) ) + 4 * ci * sizegamadot * (I_ - 3*a_)
where keisi is a dimensionless scalar ,a_ is dimensionless tensor , twoD is shear rate tensor ( dimesnion = grad velocity = 1/s ) and I_ is identity tensor(dimensionless)
although ci is dimensionless in real world but this formula makes openFoam to consider it as a dimensioned scalar.(I don't know really why it happens?!! )
however, my question is how i should convert ci in to a dimensionless scalar which can be use in the aEqn?
any help would be appreciated.
Cpro is right, sizegamadot is not dimless and this is causing the problem.
The easiest way of solving this, is by writing something as
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