Clarification Needed on LES Extrapolation Warning and SGS Model Implementation

[JhonCordova]

Hello,

I am working with LES and I would like to know specifically what this message means: 'WARNING -- Need to implement LES extrap here, see diffusion,' which appears in the getLESTerm method defined in LES.cpp. Could you please provide me with more information?

void
PeleC::getLESTerm(
  amrex::Real time,
  amrex::Real dt,
  amrex::MultiFab& LESTerm,
  amrex::Real reflux_factor)
{
  BL_PROFILE("PeleC::getLESTerm()");

  if (!do_les) {
    LESTerm.setVal(0, 0, NVAR, LESTerm.nGrow());
    return;
  }

  if (verbose != 0) {
    amrex::Print() << "... Computing LES term at time " << time << std::endl;
  }

  switch (les_model) {

  case 0:
    getSmagorinskyLESTerm(time, dt, LESTerm, reflux_factor);
    break;

  case 1:
    getDynamicSmagorinskyLESTerm(time, dt, LESTerm, reflux_factor);
    break;

  default:
    amrex::Error("Invalid les_model number.");
    break;
  }

  amrex::Print()
    << "WARNING -- Need to implement LES extrap here, see diffusion"
    << std::endl;

  // Filter the SGS source term
  if (use_explicit_filter) {
    les_filter.apply_filter(LESTerm, filtered_les_source);
    LESTerm.define(
      grids, dmap, NVAR, filtered_les_source.nGrow(), amrex::MFInfo(),
      Factory());
    amrex::MultiFab::Copy(
      LESTerm, filtered_les_source, 0, 0, NVAR, filtered_les_source.nGrow());
  }
}

Additionally, I want to implement a one equation SGS model in LES. I have seen in the PeleC documentation, specifically in the equations section, that there are two advected quantities, Ak and Bk, that can be used. How can I enable their use in PeleC? How do I define them?

Thank you.