请教rhopimpleFoam的一个问题

[yuan_neu]

15 if (pimple.transonic())
   16 {
   17     surfaceScalarField phid
   18     (
   19         "phid",
   20         fvc::interpolate(psi)
   21        *(
   22             fvc::flux(HbyA)
   23           + rhorAUf*fvc::ddtCorr(rho, U, phi)/fvc::interpolate(rho)
   24         )
   25     );
   26 
   27     MRF.makeRelative(fvc::interpolate(psi), phid);
   28 
   29     while (pimple.correctNonOrthogonal())
   30     {
   31         fvScalarMatrix pEqn
   32         (
   33             fvm::ddt(psi, p)
   34           + fvm::div(phid, p)
   35           - fvm::laplacian(rhorAUf, p)
   36          ==
   37             fvOptions(psi, p, rho.name())
   38         );
   39 
   40         pEqn.solve(mesh.solver(p.select(pimple.finalInnerIter())));
   41 
   42         if (pimple.finalNonOrthogonalIter())
   43         {
   44             **phi == pEqn.flux();//??**
   45         }
   46     }
   47 }

代码中，为什么对phi的更新是
phi == pEqn.flux();//?????????
我查阅了rhosimpleFoam，发现也是一样，实在是弄不明白

[yuan_neu]

http://blog.sina.com.cn/s/blog_97cadb820102w2h0.html
在这里找到一些回答