applications/solvers/combustion/rhoReactingFoam/UEqn.H

   1     fvVectorMatrix UEqn
   2     (
   3         fvm::ddt(rho, U)
   4       + fvm::div(phi, U)
   5       + turbulence->divDevRhoReff(U)
   6      ==
   7         rho*g
   8     );
   9
  10     UEqn.relax();
  11
  12     if (momentumPredictor)
  13     {
  14         solve(UEqn == -fvc::grad(p));
  15     }