[Struggle_Achieve]

Hello Everyone,

I have been trying to complete one of my projects from past few months but I am stuck and I have tried several things but I am unable to resolve the issue. I will be immensely grateful if I may get some help.

I have obtained the TURBULENT flow field in a vessel (tundish) and using this velocity field I was trying to solve the Residence Time Distribution (RTD) analysis using the scalarTransportFoam solver.

My first doubt:
I have read some previous posts regarding the RTD analysis using Openfoam:

ScalarTransportFoam for RTD calculations

Here it is clearly mentioned that we have to modify the existing scalarTransportFoam solver to incorporate the turbulent diffusivity. But we are assuming our tracer (scalar) to be exactly similar like the fluid. So we are taking the diffusion coefficient to be ZERO. So my question is that given I am assuming zero diffusivity shall I have to modify the solver to take turbulent diffusion also?

We have used the default scalarTransportFoam solver to produce the RTD curve. At t=0 tracer is introduced from the inlet for 5 seconds and its concentration at the outlet is measured using function patchMassFlowAverage.

What troubles me is that for some specific vessel (tundish) designs the area under the curve (concentration at outlet vs time) is coming out to be greater than 5 which is not possible physically as the area under the curve of concentration at inlet vs time is 5.

Is this inconsistency arising due to ignoring the turbulent diffusion? Or this might be due to using improper schemes?
My fvSchemes file is like:

 /*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         none; //leastSquares; //Gauss linear;
    grad(T)	    cellMDLimited leastSquares 0;
}

divSchemes
{
    default         none;
    div(phi,T)      Gauss MUSCL;//upwind; //Gauss linearUpwind grad(T);
}

laplacianSchemes
{
    default         none;
    laplacian(DT,T) Gauss linear uncorrected; //Gauss linear corrected;
}

interpolationSchemes
{
    default         limitedCubic;//SuperBee;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    T               ;
}


// ************************************************************************* //

Any help will be greatly appreciated.

Thanks and Regards,
PS