MRF equations for stress term

[ImanolGB]

Hi,

I am solving the Oldroyd-B equations under a rotating geometry using MRF.

I went through the equations and if I am not mistaken the p and U terms are solved in the standard OpenFOAM way explained in openfoam Wiki where phi flux is computed using the rotating relative velocity variable (Uᵣ) and the unknown is in the inertial frame (Uᵢ).

However, I am not able to find any references where such mixed equations are used for stress. Publications, for example (this)[https://onlinelibrary.wiley.com/doi/abs/10.1002/fld.1650210106], always refer to the stress equations computed fully with relative reference frame Uᵣ. I believe rheoTool uses Uᵣ in the flux evaluation div(phi,tau) and Uᵢ for other terms of the upper-convective. For instance,

 fvSymmTensorMatrix tauEqn
 (
    fvm::ddt(tau_)
  + fvm::div(phi(), tau_) 
  ==
    twoSymm(C)
  - fvm::Sp(1/lambda, tau_)
 );

with

 // Velocity gradient tensor
 volTensorField L = fvc::grad(U());

 // Convected derivate term
 volTensorField C = tau_ & L;

Did I understand correctly the implementation? Or am I missing something? And if I understood correctly, is there any reference where such implementation is given?

Thanks for this amazing library!!