Contact angle in Shan-Chen multi component model

[zshi6193]

Dear OpenLB,

In Shan-Chen multi-component model, I use the following methods to set up the contact angle:

BounceBack<T, DESCRIPTOR> bounceBackRhoPhase1( .2);
BounceBack<T, DESCRIPTOR> bounceBackRhoPhase2( .8);

The sum of the above two fictitious density is 1. To change them accordingly, different contact angles can be achieved. But the question is that simulation is hard to converge. For example, if I set the fictitious density for phase 2 is 0.8. Initially, it can form a droplet shape on the surface, but it continues to wet the surface until becoming flat.

I am just wondering whether I miss something when setting up the contact angle?

Thanks
Best regards,
Simon

[zshi6193]

Based on the paper (Proposed approximation for contact angles in Shan-and-Chen-type multicomponent multiphase lattice Boltzmann models, 2007), is it possible to add the adhesion force between fluid and solid for the consideration of contact angle by using “sLatticephase1.addLatticeCoupling”?

Thanks
Best regards,
Simon

[savis]

Dear Simon,

I have taken a look at the paper and I think I have some idea of how this can be implemented. Unfortunately it isn’t particularly easy.

There are several Shan-Chen lattice couplings (such as ShanChenForcedGenerator2D, for which the force is calculated here), however these all only include the fluid-fluid interactions and they will need to be edited to allow fluid-solid interactions.
Firstly, one (or two) new G interaction parameters need to be provided for the solid interaction.
Secondly, the extra contributions to the force need to be evaluated (similar to lines 133/134 in the linked code).
Finally, the extra terms would need to be included in the calculation of the force (lines 148/150).

For the extra contribution to the force an indicator for the solid boundary is needed. However I am not sure how this could be accessed within the lattice coupling (I believe you need the superGeometry). If anyone else has any idea about how to do this that would be appreciated.

Best wishes,
Sam

[zshi6193]

Dear Sam,

Thanks for your time to look into the problem. Appreciate.
I propose a new way for this problem. If the Shan-Chen model allows three components, one of components could be the boundary. A new G can be introduced to define the interaction between the boundary and the fluid. In this way, the contact angle can be achieved. Compared to define the contact angle via virtual wall density, the new proposed way can yield numerical stable results. Would you think that it can work in OpenLB?

Many thanks

Best regards,
Simon.

[savis]

Dear Simon,

To my knowledge, there is no three component implementation of the Shan-Chen model in OpenLB. So this approach would likely involve much more work than simply adding a solid interaction to the existing method.

Best wishes,
Sam

[Author]

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