[savis]

Dear nv4dll,

Are you by any chance using different values for kappa1 and kappa2? If so then this might be the cause. The reason is that if the value h1/kappa1 + h2/kappa2 != 0 then the density on the solid boundary will be different. This will then interact with the outlet causing it to become unstable.

To find the correct kappa values you can use the formula gamma = alpha/6 * (kappa1 + kappa2), where gamma is the surface tension converted into lattice units. Since you are only using two components you can therefore set kappa1 = kappa2 = 3*gamma/alpha.

Unfortunately by changing the kappa values you will also change the contact angles, so you may need to recompute the values h1 and h2.

If this isn’t the issue then please do let me know.

Best wishes,
Sam

[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

[savis]

Dear Simon,

I believe that this is because of boundary nodes that aren’t beside any inner fluid nodes. You should hopefully be able to resolve this simply using “superGeometry.clean();” after the material numbers are assigned.

Best wishes,
Sam

[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

[Author]

Posts