[jqtranus]

Hello all,

I'm a first-year student, so apologies if the question seems super simple, but I have been attempting to find an answer for at least a couple of days now.

I have been attempting to use the icoReactingMultiphaseInterFoam to simulate the freezing of a droplet on a cold substrate. However, when using either the constantAlphaContactAngle or dynamicAlphaContactAngle boundary conditions, when I run the solver it acts as if the contact angle is just 90 degrees. Upon my research I have found a similar question was asked, with no solution provided.

Here is what I have:

    
floor
    {
        type            constantAlphaContactAngle;
        theta0          60;
        limit           gradient;
        value          uniform 0;
    }

When I looked at the multiphase interfoam tutorial code (which I assumed would work similarly) the boundary condition looked like:

    leftWall
    {
        type            alphaContactAngle;
        thetaProperties
        (
            ( water air ) 90 0 0 0
            ( oil air ) 90 0 0 0
            ( mercury air ) 90 0 0 0
            ( water oil ) 90 0 0 0
            ( water mercury ) 90 0 0 0
            ( oil mercury ) 90 0 0 0
        );
        value           uniform 0;
    }

However apparently alphaContactAngle isn't a valid boundary condition for icoReactingMultiphaseInterFoam.

Can anybody help me out with this?

-EDIT:
Fixed some typos with the code block staticAlphaContactAngle -> constantAlphaContact angle
Removed uTheta

[TCS]

I haven't used this solver so I don't have an example to give you (and I'll happily stand corrected if anyone sees anything incorrect that I write), but here's a few points.

alphaContactAngle is a specific boundary condition for the multiphaseInterFoam solver. Have a look at the source code in /applications/solvers/multiphase/multiphaseInterFoam/ So that's why it's showing as not a valid boundary condition (despite the similar name).

You want to use one of the `standard' boundary conditions. You can find those in /src/transportModels/twoPhaseProperties/alphaContactAngle. staticAlphaContactAngle is not one of these. I think you want constantAlphaContactAngle. You do not need to specify uTheta for this - that is used for dynamicAlphaContactAngle. I guess how this solver works is you'll need to specify the boundary conditions for each phase relative to the air (alpha=0), but I'm not sure.

Try constantAlphaContactAngle, see if that works and let us know.

[jqtranus]

Originally Posted by TCS

I haven't used this solver so I don't have an example to give you (and I'll happily stand corrected if anyone sees anything incorrect that I write), but here's a few points.

alphaContactAngle is a specific boundary condition for the multiphaseInterFoam solver. Have a look at the source code in /applications/solvers/multiphase/multiphaseInterFoam/ So that's why it's showing as not a valid boundary condition (despite the similar name).

You want to use one of the `standard' boundary conditions. You can find those in /src/transportModels/twoPhaseProperties/alphaContactAngle. staticAlphaContactAngle is not one of these. I think you want constantAlphaContactAngle. You do not need to specify uTheta for this - that is used for dynamicAlphaContactAngle. I guess how this solver works is you'll need to specify the boundary conditions for each phase relative to the air (alpha=0), but I'm not sure.

Try constantAlphaContactAngle, see if that works and let us know.

Thanks for the response:

I forgot to remove uTheta when I changed it back from dynamicAlphaContactAngle to constant. Also the static was a mistake when I was rewriting the code for this post. I don't know how I missed that.

I did try both constantAlphaContactAngle and dynamicAlphaContactAngle. Despite what numbers I put in the theta0 the simulation still proceeds as if it was a constant contact angle of 90 degrees.

Here is my case file. I had a working droplet simulation in just InterFoam with a very simular set up so I don't know what I'm doing differently.

dropletFreezeSim2D.zip

-EDIT:
Something I noticed is that the constantAlphaContactAngle and dynamicAlphaContactAngle are designed for only two phases, while icoReactingMultiphaseInterfoam is designed for more than two, which might be the issue. Is it be possible to make some modifications to the solver to allow for the use of alphaContactAngle conditions?

[TCS]

Let me have a look at the .zip tomorrow and get back to you.

[jqtranus]

Originally Posted by TCS

Let me have a look at the .zip tomorrow and get back to you.

I was wondering if you had figured anything out, and sorry to make you spend time figuring it out.

I thought about what you said, which is setting the contact angles all relative to the alpha = 0 phase, which you said was air, but I don't think this would work in the case of 3 phases. For example if you had (solid-liquid-gas) and you specified the solid-gas and liquid-gas, you still have to specify the liquid-solid contact angle somehow. What the multiphaseInterFoam solver seems to do that the iRMIF solver doesn't is that it takes the phase pairs and corrects the boundary (which I found in the multiphaseMixture.C file).

I am currently attempting to modify the icoReactingMultiphaseInterFoam solver to use the same alphaContactAngle boundary condition that is used in the multiphaseInterFoam solver but I don't think my coding capabilities are up to par.

[TCS]

Sorry for the delay in replying. I don't see anything obvious in the zip you uploaded.

Maybe this is a silly question, but which phases are miscible? What I was thinking with contact angles with respect to air was if the inner fluids (i.e. whatever the liquid reacts to give) are miscible (?) then there's no interface. Presumably only the air interface with the other fluids, and the contact angle is implemented though a correction to the interface curvature that feeds into the Brackbill surface tension formulation in OpenFOAM. This might be the issue - as you pointed out above the constantAlphaContactAngle model is only good for two-phases. So if the input files are going to work as it, that theta0 must be only with respect to one phase I think.

With all that, I think you might have found the way forward which is to implement the alphaContactAngle boundary condition.

I will try to have a closer look at it in the next few days though.

[jqtranus]

Originally Posted by TCS

Sorry for the delay in replying. I don't see anything obvious in the zip you uploaded.

Maybe this is a silly question, but which phases are miscible? What I was thinking with contact angles with respect to air was if the inner fluids (i.e. whatever the liquid reacts to give) are miscible (?) then there's no interface. Presumably only the air interface with the other fluids, and the contact angle is implemented though a correction to the interface curvature that feeds into the Brackbill surface tension formulation in OpenFOAM. This might be the issue - as you pointed out above the constantAlphaContactAngle model is only good for two-phases. So if the input files are going to work as it, that theta0 must be only with respect to one phase I think.

With all that, I think you might have found the way forward which is to implement the alphaContactAngle boundary condition.

I will try to have a closer look at it in the next few days though.

Thanks for the reply, and no worries about the delay, since you're taking the time to help me and all.

I'm unsure if I'm interpreting what you said correctly, but icoReactingMultiphaseInterFoam only has immiscible phases. icoReactingMultiphaseInterFoam is for "N incompressible, non-isothermal immiscible fluids with phase-change".

Like you said, I think the way forward is implementing the alphaContactAngle boundary condition.

[rokm]

Hello all,


sorry for opening an old thread, but has anybody found a solution for the problem of contact angle in icoReactingMultiphaseInterFoam?


I have tried to solve the problem by adding alphaContactAngle to icoReactingMultiphaseInterFoam, but the solver still acts as there is 90 degree contact angle on the walls. I am using OF v2112.


A solution or any advice would be very appreciated.


Thanks!