In which operation should I apply the Bounce back conditions ?

[Bolt]

Hi, rnDear all, rnrnI’m simulating the heat transfer in a cavity which contains two heated obstacles, rnMy problem is where should I add the (Thermal) bounce back condition(solid-fluid) in the stream operation or in the collision one, 😕 🙁 rnMore, the LBM Algorithm in oure code is in this order : rnrn1-Initialization rn2-Stream rn3-Boundary conditions rn4-Macroscopic proporties rn5-Collision rnrnWould you mind helping me or advising me please? rnrnrnBest regards,rn

[mathias]

Dear Bolt,rnrn I would include it in the stream step.rnrnMathias

[Bolt]

Thank you for your reply Mathias,rnCould you tell me why, please ?rnrnBolt

[mathias]

Dear Bolt,rnrn The reason is the motivation behind Bounce Back: a particle moving towards the wall, coliding with it and being reflexted. So you can also include it in your step 3. It really depends on how you have implemented your LBM, e.g. if you a working with ghost cells.rnrnMathias

[Bolt]

Thank you so much Mathias,rnWhen I applied the BB conditions for the Hydrodynamic field,rnThe streamlines that I have finded are not good,rnEspecially, near the obstacle like a thick line (perturbation),rnCould you tell me why, please

[mathias]

Dear Bolt,rnrn Depending on actual shape of the obstracle Bounce Back might just 1st order accurate. You will get better results if you refine the mesh and a better order with Bouzidi’s boundary conditions. We are currently working on Bouzidi’s boundary conditions.rnrnMathias

[Bolt]

Thank you so much Mathias,

[asalghazal]

Quote:

Quote from Bolt on August 16, 2012, 17:00rnThank you for your reply Mathias,rnCould you tell me why, please ?rnrnBolt

[mathias]

Have a look at: http://dx.doi.org/10.1063/1.1399290 rnrnMathias

[GengLiu]

Quote:

Quote from mathias on August 28, 2012, 05:13rnDear Bolt,rnrn Depending on actual shape of the obstracle Bounce Back might just 1st order accurate. You will get better results if you refine the mesh and a better order with Bouzidi’s boundary conditions. We are currently working on Bouzidi’s boundary conditions.rnrnMathias

rnrnWell, I did not know that you are still using wet bounce back, Mathias. As I told you in Changchun, it should be dry bouceback, or half-way bounceback, proved 2nd order accurate by Ladd el (if I am right). The accuracy depends on how you draw the geometry.

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