[zqlhzx]

Hi foamers,
I found a strange problem with the two difference define of psi in createField.H.
one is

const volScalarField& psi=thermo.psi();

another one is

const volScalarField psi 
    ( 
        IOobject 
        ( 
            "psi", 
            runTime.timeName(), 
            mesh, 
            IOobject::NO_READ, 
            IOobject::NO_WRITE 
        ), 
        thermo.psi() 
    );

If I use the first one :"const volScalarField& psi=thermo.psi();",then I run my case,it gave me error and just gave me the available volScalarField :

FOAM FATAL ERROR:

request for volScalarField psi from objectRegistry region0 failed
available objects of type volScalarField are

57
(
ignite
thermo:mu
thermosi
N2
K
fvar_0
CH2CO
K_0
C2H4
C3H8
alphaLam
rho
C2H6
CO2
Dt
C2H2
CH3COCH3
H2O2
O2
sqrt(((2*symm(grad(U)))&&symm(grad(U))))
p_rgh
H2
(1|A(U))
fmix_0
dpdt
gh
fort_0
delta
CH4
ha
thermosi_0
.......... and so on (I just list some available volScalarField)
)

Dose it mean that volScalarField psi is need and I have not define?
So ,I define psi using the latter way:

const volScalarField psi 
    ( 
        IOobject 
        ( 
            "psi", 
            runTime.timeName(), 
            mesh, 
            IOobject::NO_READ, 
            IOobject::NO_WRITE 
        ), 
        thermo.psi() 
    );

then I run my case ,there is no error and my case can be run.However,I found sovles in OF define psi as the first way:"const volScalarField& psi=thermo.psi();".
For the error,I found it appears when my case run at the location where I use red words in the following pEqn.H.(I use OF2.2.2 )

{ 
 rho = thermo.rho(); 
    //psi = thermo.psi(); 
    // Thermodynamic density needs to be updated by psi*d(p) after the 
    // pressure solution - done in 2 parts. Part 1: 
 thermo.rho() = thermo.rho()-psi*p_rgh; 
    volScalarField rAU(1.0/UEqn.A()); 
    surfaceScalarField rhorAUf("Dp", fvc::interpolate(rho*rAU)); 
    volVectorField HbyA("HbyA", U); 
    HbyA = rAU*UEqn.H(); 
    surfaceScalarField phig(-rhorAUf*ghf*fvc::snGrad(rho)*mesh.magSf()); 
    surfaceScalarField phiHbyA 
    ( 
        "phiHbyA", 
        fvc::interpolate(rho) 
       *( 
            (fvc::interpolate(U) & mesh.Sf()) 
          + fvc::ddtPhiCorr(rAU, rho, U, phi) 
        ) 
      + phig 
    ); 
    fvOptions.relativeFlux(fvc::interpolate(rho), phiHbyA); 
 
    fvScalarMatrix p_rghDDtEqn 
    ( 
        fvc::ddt(rho) + psi*correction(fvm::ddt(p_rgh)) 
      + fvc::div(phiHbyA) 
      == 
        fvOptions(psi, p_rgh, rho.name()) 
    ); 
 
    while (pimple.correctNonOrthogonal()) 
    { 
        fvScalarMatrix p_rghEqn 
        ( 
            p_rghDDtEqn 
          - fvm::laplacian(rhorAUf, p_rgh) 
        ); 
 
        fvOptions.constrain(p_rghEqn); 
 
        p_rghEqn.solve(mesh.solver(p_rgh.select(pimple.finalInnerIter()))); 
 
        if (pimple.finalNonOrthogonalIter()) 
        { 
            // Calculate the conservative fluxes 
            phi = phiHbyA + p_rghEqn.flux(); 
 
            // Explicitly relax pressure for momentum corrector 
            p_rgh.relax(); 
 
            // Correct the momentum source with the pressure gradient flux 
            // calculated from the relaxed pressure 
            U = HbyA + rAU*fvc::reconstruct((phig + p_rghEqn.flux())/rhorAUf); 
            U.correctBoundaryConditions(); 
            fvOptions.correct(U); 
            K = 0.5*magSqr(U); 
        } 
    } 
    p = p_rgh + rho*gh; 
    // Second part of thermodynamic density update 
    thermo.rho() = thermo.rho()+psi*p_rgh; 
    if (thermo.dpdt()) 
    { 
        dpdt = fvc::ddt(p); 
    } 
    #include "rhoEqn.H" 
    #include "compressibleContinuityErrs.H" 
}

I think psi can not work at the pressure equations.But it is so strange why it did not work when I use the first way to define psi and it works when I use the latter way?
Does some one can help to explain the problem?And how can I use the first way to define psi?Because OF use the first way to define psi,I also want to do like that.
Thanks in advance!