[zshi6193]

Dear Aurelio,
Thanks for your suggestion, I am just wondering about how to set the state of fluid in OpenLb for example if I am using single or two component Shan-Chen model.

Best regards,
Simon

[zshi6193]

Dear Max,

You mention the force field in OpenLB is actually a force over reference density. For multi-phase flow, I have two phases (liquid and vapor via using single component Shan-Chen model). If I define a force field (an acceleration) into the whole domain, will this method still works?
I am just thinking that vapor tends to have very small acceleration because of very small density. Or this method can only be used two-component Shan-Chen model.

Thanks for your help.
Simon

[zshi6193]

Dear Dr. Mathias,

Thanks for your quick response. I think that I find a way to solve the problem but want to double-check with you.

In two compartment Shan-Chen model(oil with rho=0.8 inside the water with rho=1), I try different g. When g is 3.5, the simulation can converged in around 40000 steps (the simulation domain is 100*100*60, the initial oil drop size is 40*40*40, periodic boundary in x and y, the top and bottom is set up to be bounce-back solid wall with a density (0.6 for latticeOil, 0.4 for latticeWater)). I increase g for larger repulsive force because I find that there are significant miscibility if g is 3 or less. When g is 3, the volume of formed droplet tends to decrease with the fixed contact angle and it takes very long time to converge. In that case, if the initial volume of droplet is small, the droplet tends to disappear after many iterations.To be concluded, It is very hard to achieve the mass conservation if g is 3 or less. Choosing g of 3.5 may works for setting up the contact angle in 3D.

Thanks for your response.
Best regards,
Simon

[zshi6193]

Dear Dr Mathias,

Thanks for your reply and suggestion. After I increase the mesh size, the problems are partly solved.

Best regards,
Simon

[zshi6193]

Dear Mathias,

Sorry I have difficulty in uploading the image.
Here are the dropbox links of of my geometry. Thanks for your time. The highlight is the another boundary problem when two particles are close to each other. The multiphase model that I used is the free energy one.
Thanks for your help.

Best regards,
Simon.
https://www.dropbox.com/s/cjftfooi4i85qbn/1.PNG?dl=0
https://www.dropbox.com/s/k6k4v8csgskjmrr/2.PNG?dl=0

• This reply was modified 5 years, 2 months ago by zshi6193.

[zshi6193]

• This reply was modified 5 years, 2 months ago by zshi6193.

[zshi6193]

• This reply was modified 5 years, 2 months ago by zshi6193.
• This reply was modified 5 years, 2 months ago by zshi6193.
• This reply was modified 5 years, 2 months ago by zshi6193.

[zshi6193]

• This reply was modified 5 years, 2 months ago by zshi6193.

[zshi6193]

• This reply was modified 5 years, 2 months ago by zshi6193.

[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.

[zshi6193]

Dear Sam,

Thanks for your reply. I try to use “superGeometry.clean” and superGeometry.innerClean”. The same error comes out. But in fact, it seems this error doesn’t affect the results.

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

[zshi6193]

Hi Max and Aurelio,

Really thanks for your help. It helps me a lot.

I will try Max’s suggestion and see how it goes. So Can I say that there is no way to set the pressure boundary for both inlet and outlet in Shan-Chen multiphase model?

Best regards,
Simon

[zshi6193]

Dear Max,

Sorry that I didn’t express myself clearly. I would like to test whether the system can reach equilibrium without gravity. So the middle of the domain is filled with oil and the rest part of the domain is filled with water. I set the same density for oil and water. If I use the following code, the system should reach the equilibrium but unfortunately, it didn’t. Would you think that the following codes are correct for the constant pressure boundary at both inlet and outlet?
Also, a very small question, do we need add ” sLatticeWater.addLatticeCoupling(superGeometrytest, 3(inlet), couplingtest, sLatticeOil ) for the inlet and outlet.

Thank you.

Code:
slatticeWater.defineRho(supergeometry,3(inlet),rhowater)
slatticeOil.defineRho(supergeometry,3(inlet),zero) (not sure whether we need to set the pressure for oil is zero)
slatticeWater.defineRho(supergeometry,4(outlet),rhowater)
slatticeOil.defineRho(supergeometry,4(outlet),zero).
(applied in each step)

[zshi6193]

Dear Max,

Thanks for your reply. Much appreciated.
I am sorry that I have one more question regarding the pressure boundary used in Shan-Chen two compartment multiphase model. To set the pressure inlet and pressure outlet, I used the following methods:
slatticeWater.defineRho(supergeometry,3(inlet),rhowater)
slatticeOil.defineRho(supergeometry,3(inlet),zero)
slatticeWater.defineRho(supergeometry,4(outlet),rhowater)
slatticeOil.defineRho(supergeometry,4(outlet),zero).
(I applied above four codes every iteraction to keep the constant pressure)
Alternatively, I also try:
Bcwater.addPressureBoundary(supergeometry,3(inlet),omega)
BcWater.addPressureBoundary(supergeometry,4(outlet),omega)
slatticeOil.defineRho(supergeometry,3(inlet),zero).
slatticeOil.defineRho(supergeometry,4(outlet),zero).

The middle part of the domain is filled with oil and the rest is filled with water. But under above set up, the equilibrium state can not be achieved. The pre-filled oil layer moves downwards.
I am not sure that I set up the boundary conditions correctly or not? .Could you help me to check it? Ideally, at the same pressure at the top and bottom (no pressure gradient), the oil in the middle part should be stable.

Thank you very much.
Simon

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