CFD Online Discussion Forums - Virtual Mass Force Implementation in icoLagrangianFoam- foam

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ali_atrian

October 27, 2014 11:47

Virtual Mass Force Implementation in icoLagrangianFoam- foam_exd 3.0

Hello Dear openFOAMers
I am a bigginer to openFoam and I want to activate virtualMass force in solver icoLagrangianFoam. so in the file constant/kinematicCloudProperties I enable the force and also add a line to determine Cvm value:

Code:

particleForces

{

    gravity         on;

    virtualMass     on;

    Cvm                    0.5;

    pressureGradient on;

        

}

but I receive the error:

Code:

--> FOAM FATAL ERROR: 

Not implemented

    From function Foam::particleForces::calcCoupled(...) - virtual mass force

    in file particleForces/particleForces.C at line 153.

FOAM aborting

Aborted (core dumped)

the error is related to the following lines of src/lagrangian/intermediate/particleForces/particleForces.C:

Code:

Foam::vector Foam::particleForces::calcCoupled

(

    const label cellI,

    const scalar dt,

    const scalar rhoc,

    const scalar rho,

    const vector& Uc,

    const vector& U

) const

{

    vector Ftot = vector::zero;

    // Virtual mass force

    if (virtualMass_)

    {

        notImplemented

        (

            "Foam::particleForces::calcCoupled(...) - virtual mass force"

        );

//        Ftot += Cvm_*rhoc/rho*d(Uc - U)/dt;

    }

does anyone know what i ave to do?

I thankfuuullly apreciate any help

ali_atrian

October 30, 2014 03:40

some one give me just a small hint pleaseee
in file particleForces.C, I uncommented the line:

Code:

Ftot += Cvm_*rhoc/rho*d(Uc - U)/dt

but I received the error:

Code:

particleForces/particleForces.C: In member function ‘Foam::vector Foam::particleForces::calcCoupled(Foam::label, Foam::scalar, Foam::scalar, Foam::scalar, const vector&, const vector&) const':

particleForces/particleForces.C:154:39: error: 'd' was not declared in this scope

what shoul i do? is there any toutorial shed lights on my problem
in openfoam 2.3 and 2.1 i didt find any library file including the virtual mass formula as included in foam-exd 3.0 and any other tutorials in foam extend 3.1 lead to the same errors when virtualMass" is "on"
I Greatfuuuly appreciate any help

ali_atrian

November 6, 2014 02:26

no help on virtual mass implemention to foam-exd 3.0??!!

kalyan

November 6, 2014 09:15

Hi,

even im struck with VIrtualMass. im using openFoam-2.3.x and defined VirtualMass in particle force as

virtualMass
{
Cvm 0.5;
}

but i get a error :

request for volVectorField U from objectRegistry region0 failed available objects of type volVectorField are 1(U.air).

if i remove virtualMass , then simualtion goes fine.. im not sure what this error is..

Regards,
Kalyan

ali_atrian

November 8, 2014 11:59

I got where the problem arises from:
I used "src/finiteVolume/finiteVolume/fvc" library and change the virtual mass formulation as:

Code:

Ftot += Cvm_*rhoc/rho*fvc::ddt(Uc-U);

but i found that all the class templates defined in fvcDdt.C have their output formats in something like volVectorField! :

Code:

    template<class Type>

    tmp<GeometricField<Type, fvPatchField, volMesh> > ddt

    (

        const GeometricField<Type, fvPatchField, volMesh>&

    );

while we need 'vector' format for 'Ftot' (in particleForces.C) :

Code:

Foam::vector Foam::particleForces::calcCoupled

(

    const label cellI,

    const scalar dt,

    const scalar rhoc,

    const scalar rho,

    const vector& Uc,

    const vector& U

) const

{

    vector Ftot = vector::zero;

so, we need to define a class template something like:

Code:

   /* template<class Type>

    tmp< vector > ddt

    (

        const vector&

    );

*/

and thats the way we can implement virtual mass force (I think so)
I myself have not ever defined any template so I neglected annny eddition because it seems hard for me to go through this way and now im going to simulate my problem using DPMFoam in OF230 :o
however, I appreciate any comment whether on my findings or about template defenition for this problem
GoOoD LucK

ali_atrian

November 8, 2014 12:05

Quote:

Originally Posted by kalyan (Post 517714)

I will be engaged in virtual mass force in OF230 so sooon, (as I mentioned in prior post) so I will talk about that if there be any comment to share with u

oswald

November 10, 2014 04:34

In order to calculate the virtual mass force, I added a new member to kinematicParcel called "Urelold". As the name suggests, it is the relative velocity between fluid and particle at the previous time step. To calculate d(Uc-Up)/dt, you can then use the old and the current relative velocities and the current time step and you don't need fvc::ddt(Uc-U) anymore.

ali_atrian

November 10, 2014 06:22

implementation of acceleration in VM force

Hello Oswald
first of all i really thank you to give me some points
Maybe i can't get what you exactly mean, but :
1) here we nead (Uc-U) not an average between particle and fluid velocities!
2) in the formula, we have to insert the acceleration (not velocity) so why do you say

Quote:

you can then use the old and the current relative velocities

?

- can u explane a bit more on code implementation (the code that u say it can be used instead of

Code:

fvc::ddt(Uc-U)

and does it need any other changes in any other files in libs or solver ??
Best Regards

oswald

November 10, 2014 07:00

I hope I got you right. The code fvc::ddt(Uc-U) can be seen as the change of the relative particle velocity (Uc-U) per time, i.e. d(Uc-U)/dt. Approximately this is the same as [(Uc-U)_current - (Uc-U)_old]/deltaT. (Uc-U)_current ist the current difference between particle and velocity fluid and can be calculated with the current values. I simply store this value as the value for (Uc-U)_old for the next time step. The change over time is then simply calculated by dividing the difference of the relative velocities by the current deltaT.

A disadvantage here is that you are not free to choose a different interpolation scheme.

The Urelold-value is stored in the kinematicParcel-class like U, d, rho and so on.

ali_atrian

November 11, 2014 03:16

Hello Oswald
I really appreciate all your guidance
Its now clear for me :o
Best Regards

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