[Fahmida]

Hello everyone,
I am running my simulation on Nucleate Boiling. My bubble has been created successfully like a semi-sphere on a heated surface but for some reason it is not increasing its size. What can be the reason behind this?

Any idea would be appreciated. Thank you.

[saddy]

what solver are you using ?

[Bali]

Originally Posted by Fahmida

Hello everyone,
I am running my simulation on Nucleate Boiling. My bubble has been created successfully like a semi-sphere on a heated surface but for some reason it is not increasing its size. What can be the reason behind this?

Any idea would be appreciated. Thank you.

hi FaRa,
could you upload your case files so that we can see where the problem is

[Fahmida]

hi Saddy,

Thank you for your response. I am using interThermalPhaseChangeFoam solver which has been extended from interFoam.

Here is the paper link:

https://www.sciencedirect.com/scienc...52711016300309

[Fahmida]

Hi Bali, thank you for your response.

Here is my blockMesh file:

convertToMeters 1;

vertices
(
    (0 0 0)
    (0.031 0 0)
    (0.031 0.031 0)
    (0 0.031 0)
    (0 0 0.031)
    (0.031 0 0.031)
    (0.031 0.031 0.031)
    (0 0.031 0.031)
);

blocks
(
     hex (0 1 2 3 4 5 6 7) (120 120 120) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    bottom
    {
        type wall;
        faces
        (
            (1 5 4 0)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (3 7 6 2)
        );
    }
    walls
    {
        type wall;
        faces
        (
            (0 4 7 3)
            (2 6 5 1)
            (0 1 2 3)
            (4 5 6 7)
        );
    }
);

mergePatchPairs
(
);

Here is the toposetDict:

actions
(
    {
        name c0;
        type cellSet;
        action new;
        source sphereToCell;
        sourceInfo
        {
            centre (0.0155 0 0.0155);
            radius 0.001;
        }
    }

    {
        name c0;
        type cellSet;
        action delete;
        source boxToCell;
        sourceInfo
        {
            
                  box (0.0145 -0.001 0.0145) (0.0165 0 0.0165);
        }
    }

);

Here is the setFieldDict:

defaultFieldValues
(
        volScalarFieldValue alpha1 0
        volScalarFieldValue T 559.95
        volVectorFieldValue U (0 0 0)
);

regions
(


   boxToCell
    {
        box (0 0 0) (0.031 0.026 0.031);
        fieldValues
        (
            volScalarFieldValue alpha1 1
            volScalarFieldValue T 559.95
            volVectorFieldValue U (0 0 0)
        );
    }
   
    cellToCell
    {
        set c0;

        fieldValues
        (
            volScalarFieldValue alpha1 0
            volScalarFieldValue T 559.95
            volVectorFieldValue U (0 0 0)
        );
    }
);

ParaView file is also attached.

Here, I would like to mention that I was able to grow the bubble size when performing in 2D with meshes of 150x150. For 3D, I have tried several meshes upto 120x120x120 with different values of Evaporation threshold number but the bubble size did not increase. I think the mesh of 150x150x150 may solve the issue. But since I am performing my simulation on my laptop with only 6 cores parallel processing, it is not possible for me to turn my pc on for a week.

So any alternate suggestion is needed.

[Fahmida]

Hello everyone, I came out successfully in growing my bubble .

Now I have got the bubble detachment time by watching it in paraview. But I also need to calculate the detachment diameter in controlDict. Does anyone have any idea how to do this?

[Fahmida]

I have been able to calculate the vapor surface area for each timestep using swak4foam. But this is including the vapor over the liquid surface . Is there any way to remove them?

[saj216]

Hi Fahmida,

I am also using the interThermalPhaseChangeFoam framework for modelling bubble sliding. I was curious what boundary conditions for the p-rgh field you have been using for your simulations.

Kind regards,

Sam

[Fahmida]

Hello,

In my computational domain consisting air and liquid has a fixedFluxPressure boundary condition for the inlet and side walls and a total pressure with p0 0 for the outflow.

[saj216]

Thanks,

Did you find out why the bubble size did not increase in your simulation?

[Fahmida]

I had to reduce the domain size and increase the evaporation threshold number although I am not clear enough how the evaporation number was effecting this issue.

[saj216]

Thank you for the help.

How did you initialise the perfect bubble shape especially on a perfectly smooth surface.

Sorry for asking, I'm not very good at OpenFoam

[Bali]

Originally Posted by saj216

Thank you for the help.

How did you initialise the perfect bubble shape especially on a perfectly smooth surface.

Sorry for asking, I'm not very good at OpenFoam

I think there is a tutorial case in interThermalPhaseChangeFoam for single bubble growth.
BTW, the solver evapVOFHardt based on of231 is also useful for bubble growth simulation.
It should be noted that spurious current might be an issue in this kind of simulation

[saj216]

Hi,

Thanks, yeah there is but the simulation relies on a cavity in the mesh rather than a smooth surface. Btw have you had any issues changing boundary conditions of the thermalphasechangefoam solver. When I have the simulation has quickly collapsed.

For example for a vapour surrrounded in a superheated liquid scenario. I can provide for detail if required. Thanks again.

[Bali]

Originally Posted by saj216

Hi,

Thanks, yeah there is but the simulation relies on a cavity in the mesh rather than a smooth surface. Btw have you had any issues changing boundary conditions of the thermalphasechangefoam solver. When I have the simulation has quickly collapsed.

For example for a vapour surrrounded in a superheated liquid scenario. I can provide for detail if required. Thanks again.

Hi, Sam

it will be good to check your case if can upload it.

Best

[saj216]

Hi Bali,

Sorry, for the late reply. This is the common error, I repeatedly get. I assume it is an issue of my pressure boundaries. If you understand why, could you explain to me as simply as possible .

--> FOAM FATAL IO ERROR:
wrong token type - expected Scalar, found on line 0 the word 'nan'

file: /home/joseph/OpenFOAM/joseph-2.4.0/run/CFD-PC-master/CFD-PC/interThermalPhaseFoam/tutorials/VapourGrowthWithoutLayer/system/data.solverPerformance.p_rgh at line 0.

From function operator>>(Istream&, Scalar&)
in file lnInclude/Scalar.C at line 93.

Thank you for the help.

Sam

[Bali]

Originally Posted by saj216

Hi Bali,

Sorry, for the late reply. This is the common error, I repeatedly get. I assume it is an issue of my pressure boundaries. If you understand why, could you explain to me as simply as possible .

--> FOAM FATAL IO ERROR:
wrong token type - expected Scalar, found on line 0 the word 'nan'

file: /home/joseph/OpenFOAM/joseph-2.4.0/run/CFD-PC-master/CFD-PC/interThermalPhaseFoam/tutorials/VapourGrowthWithoutLayer/system/data.solverPerformance.p_rgh at line 0.

From function operator>>(Istream&, Scalar&)
in file lnInclude/Scalar.C at line 93.

Thank you for the help.

Sam

hi Sam,

I have checked your files. Here some points:

1. why the "base" boundary is applied with "symmetry"? if it is a base wall boundary, "symmetry" is not appropriate.

2. I guess you can not use "fixedvalue 0" for "top" and "right" boundary at the same time. one of them could be changed into "zeroGradient"

[saj216]

Sorry for the confusion, the base in this case is symmetry because the bubble is initialised in the simulation so that it is a 1/4 of a bubble. So that the computing requirement can be reduced.

Okay I will try that and come back to you if it works.

Thanks again.

[Bali]

Originally Posted by saj216

Sorry for the confusion, the base in this case is symmetry because the bubble is initialised in the simulation so that it is a 1/4 of a bubble. So that the computing requirement can be reduced.

Okay I will try that and come back to you if it works.

Thanks again.

OK. but I guess "symmetryPlane" might be better

[saj216]

Sad news, your suggestions didn't work. The symmetryPlane BC on the base affects the axisymmetric setup and prevents it running. Do you have any other suggestions ?