[Berilmun]

Hi everyone,


I am trying to implement the following equation within OpenFOAM (Ua is the adjoint velocity) :

- Ua+Ua U- ( Ua) U + pa = -2 U


I tried the following implementation but I'm not sure it computes the adjoint equation above

       

  volTensorField gradU (fvc::grad(U));
  volVectorField adjointTransposeConvection2(gradU.T() & Ua); 

  tmp<fvVectorMatrix> tUaEqn
  (
        fvm::div(-phi, Ua)
        +fvm::Sp(fvc::div(phi),Ua)
        + adjointTransposeConvection2
        +turbulence->divDevReff(Ua)
         ==
         fvOptions(Ua)
            );

            fvVectorMatrix& UaEqn = tUaEqn.ref();

            UaEqn.relax();

            fvOptions.constrain(UaEqn);

            solve(UaEqn == -fvc::grad(pa)-2*tau*fvc::laplacian(nu,U));

Do you have any tip about this implementation ?



Thanks in advance.
Berilmun

[massive_turbulence]

Originally Posted by Berilmun

Hi everyone,


I am trying to implement the following equation within OpenFOAM (Ua is the adjoint velocity) :

- Ua+Ua U- ( Ua) U + pa = -2 U


I tried the following implementation but I'm not sure it computes the adjoint equation above

       

  volTensorField gradU (fvc::grad(U));
  volVectorField adjointTransposeConvection2(gradU.T() & Ua); 

  tmp<fvVectorMatrix> tUaEqn
  (
        fvm::div(-phi, Ua)
        +fvm::Sp(fvc::div(phi),Ua)
        + adjointTransposeConvection2
        +turbulence->divDevReff(Ua)
         ==
         fvOptions(Ua)
            );

            fvVectorMatrix& UaEqn = tUaEqn.ref();

            UaEqn.relax();

            fvOptions.constrain(UaEqn);

            solve(UaEqn == -fvc::grad(pa)-2*tau*fvc::laplacian(nu,U));

Do you have any tip about this implementation ?



Thanks in advance.
Berilmun

Did you mix up Nabla and Delta for this part fvm::div(-phi, Ua) or the Laplacian and Divergence?

[Berilmun]

The convection term - Ua is described by the term turbulence->divDevReff(Ua) in the code. The term fvm::div(-phi,Ua) is only modelling - ( Ua) U. That's the point on which i'm not sure in my implementation.

Thank you for the reply.

[massive_turbulence]

Originally Posted by Berilmun

The convection term - Ua is described by the term turbulence->divDevReff(Ua) in the code. The term fvm::div(-phi,Ua) is only modelling - ( Ua) U. That's the point on which i'm not sure in my implementation.

Thank you for the reply.

The call to "turbulence->divDevReff(Ua) " is more than just Ua

template<class BasicTurbulenceModel>
 Foam::tmp<Foam::fvVectorMatrix>
 Foam::linearViscousStress<BasicTurbulenceModel>::divDevRhoReff
 (
     volVectorField& U
 ) const
 {
     return
     (
       - fvc::div((this->alpha_*this->rho_*this->nuEff())*dev2(T(fvc::grad(U))))
       - fvm::laplacian(this->alpha_*this->rho_*this->nuEff(), U)
     );
 }

Above code is line 91 from https://www.openfoam.com/documentati...8C_source.html

nuEff() is the effective viscosity.

dev2 is line 115 from https://www.openfoam.com/documentati...8C_source.html

Just use -fvm::laplacian(nu, Ua).

[Berilmun]

Originally Posted by massive_turbulence

The call to "turbulence->divDevReff(Ua) " is more than just Ua

template<class BasicTurbulenceModel>
 Foam::tmp<Foam::fvVectorMatrix>
 Foam::linearViscousStress<BasicTurbulenceModel>::divDevRhoReff
 (
     volVectorField& U
 ) const
 {
     return
     (
       - fvc::div((this->alpha_*this->rho_*this->nuEff())*dev2(T(fvc::grad(U))))
       - fvm::laplacian(this->alpha_*this->rho_*this->nuEff(), U)
     );
 }

Above code is line 91 from https://www.openfoam.com/documentati...8C_source.html

nuEff() is the effective viscosity.

dev2 is line 115 from https://www.openfoam.com/documentati...8C_source.html

Just use -fvm::laplacian(nu, Ua).

I'm working without turbulence model. I put "laminar" in my turbulenceProperties dictionary, so turbulence->divDevReff(Ua) will give me the same results than fvm::laplacian(Ua) ? I'm not right? I tried both and it gives me the same results. But you are right, it's better to put directly -fvm::laplacian(Ua). Thanks.
Do you have a tip to modeling the term ( Ua)U?

[massive_turbulence]

Originally Posted by Berilmun

I'm working without turbulence model. I put "laminar" in my turbulenceProperties dictionary, so turbulence->divDevReff(Ua) will give me the same results than fvm::laplacian(Ua) ? I'm not right? I tried both and it gives me the same results. But you are right, it's better to put directly -fvm::laplacian(Ua). Thanks.
Do you have a tip to modeling the term ( Ua)U?

My guess is it would be something like this fvm::Sp(fvc::laplacian(Ua), U)?

from here Understanding fvm::Sp()

What exactly is that term by the way, is Ua the flux?