Hello!

I am adjusting the CHT tutorial for OpenFOAM and Nutils. I have 2 questions about this.

The first is about OpenFOAM. I am using the buoyantBoussinesqSimpleFoam solver, since i want to solve the heat transfer in a turbulent fluid. (i have neglected the buoyancy term by putting the gravity to 0 and the buoyancy by putting beta to 0). I have tested this with a constant heat flux on the ‘interface’ boundary only in OpenFOAM and compared it to ansys, which validated the case. Now i am trying to run it with preCICE and get the heat flux from Nutils (I am not yet using the solver, but I first want to exchange a constant value from nutils to see if it works), however i get an error i do not know how to solve. It states:

```
-> FOAM Warning :
From void adapterInfo(std::string, std::string)
in file Utilities.C at line 50
Error (deferred - will exit later) in the preCICE adapter:
Error in the preCICE adapter:
Cannot find the Prandtl number in preciceDict/CHT using the name Pr
```

I do state the Prandtl number however in my transportProperties. Do you maybe know what i am doing wrong here? I have left the xml file untouched, since i want to interchange the heat flux.

The second question is about the nutils part.

The heat flux is computed using:

```
fluxvalues = res.eval(lhs0=lhs0, lhs=lhs, dt=dt)
writedata = couplingsampleCC.eval('-flux' @ ns, fluxdofs=fluxdofs(fluxvalues))
```

However when you evaluate the residual of the weak form, it should be (close to) 0? I don’t see how this computes the heat flux.

Thank you for your time!

Kind regards,

Cars