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Drag coefficient implementation

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Old   November 24, 2020, 12:02
Default Drag coefficient implementation
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Sumit Peh
Join Date: Oct 2018
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Hi Foamers

I would like to apply equations of other Drag coefficient in 4 conditions of Renold's number.
[Re<1 // 1<Re<100 // 100<Re<1000 // Re>1000]

SchillerNaumann has 2 conditions of Re which are Re<1000 and Re>1000
Here is the SchillerNaumann code on ~dragModels
I supposed neg(Re - 1000) is this Re<1000 condition and pos0(Re - 1000) is the Re>1000.

Code:
{
    volScalarField Re(max(Ur*phase1_.d()/phase2_.nu(), scalar(1.0e-3)));
    volScalarField Cds
    (
        neg(Re - 1000)*(24.0*(1.0 + 0.15*pow(Re, 0.687))/Re)
      + pos0(Re - 1000)*0.44
    );

    return 0.75*Cds*phase2_.rho()*Ur/phase1_.d();
}
Is there a way to write code for more than 2 conditions ?

As my imagination, I guess maybe my case would be
Code:
{
    volScalarField Re(max(Ur*phase1_.d()/phase2_.nu(), scalar(1.0e-3)));
    volScalarField Cds
    (
        neg(Re - 1)*(Equation1)
      + neg1(Re - 100)*(Equation2)
      + neg100(Re - 1000)*(Equation3)
      + pos0(Re - 1000)*(Equation4)
    );

    return 0.75*Cds*phase2_.rho()*Ur/phase1_.d();
}
Please confirm if i'm right and please correct if i'm wrong.

Thanks in advanced

James
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