Vaggelis Papoutsis authored Oct 07, 2021 and Andrew Heather committed Jun 10, 2022

- ATCstandard, ATCUaGradU:
  the ATC is now added as a dimensioned field and not as an fvMatrix
  to UaEqn. This get rid of many unnecessary allocations.

- ATCstandard:
  gradU is cached within the class to avoid its re-computation in
  every adjoint iteration of the steady state solver.

- Inlined a number of functions within the primal and adjoint solvers.
  This probably has a negligible effect since they likely were inlined
  by the compiler either way.

- The momentum diffusivity at the boundary, used by the adjoint boundary
  conditions, was computed for the entire field and, then, only the
  boundary field of each adjoint boundary condition was used. If many
  outlet boundaries exist, the entire nuEff field would be computed as
  many times as the number of boundaries, leading to an unnecessary
  computational overhead.

- Outlet boundary conditions (both pressure and velocity) use the local
  patch gradient to compute their fluxes. This patch...