Beginners Aid needed – Boundary Conditions
OpenLB – Open Source Lattice Boltzmann Code › Forums › on Lattice Boltzmann Methods › General Topics › Beginners Aid needed – Boundary Conditions
- This topic has 2 replies, 2 voices, and was last updated 10 years, 9 months ago by mathias.
-
AuthorPosts
-
January 7, 2014 at 10:13 am #1749jieeshtkerMember
Hi folks,rnrnI am trying to set up a LB-simulation to simulate a pipe flow and I am experiencing several problems. I hope, you can help me in an understandable (not heavy formula using) way.rnrnFirst and most important question set:rnWhat should I do with any walls? I understand there are a lot of different approaches (bouncing back, inamuro, free slip, no slip, complex things, …) – but I fail programming any of these. As far as I understand, for a simple pipe flow I need a bouncing back condition.rnrnIs this still right?rnrnIf so, all I have to do is to take the distribution functions pointing towards the wall (e.g. pointing North, Northeast, Northwest) and put them into the wall (South, Southeast, Southwest). [This ought to be free slip or what it is called.] Now, if I switch east and west I should have no-slip.rnrnIs this still right?rnrnAnd then, what do I do if an obstacle is to be simulated? There could be corners of which I have absolutely no clue what to do with them.rnrnrnrnTo the not critical questions:rnrnIs there any way to set boundary conditions by defining macroscopic parameters (e.g. von Neumann, Dirichlet)?rnrnrnIs there a way, to realize different viscosities? I think, viscosity is only used in the collision, but can I just use different (and chaning) viscosities in a single cell (and keep conservation of mass)?rnrnMany thanks for your time and answers.
January 20, 2014 at 4:14 pm #2133mathiasKeymasterQuote:Quote from jieeshtker on January 7, 2014, 10:13rnHi folks,rnrnI am trying to set up a LB-simulation to simulate a pipe flow and I am experiencing several problems. I hope, you can help me in an understandable (not heavy formula using) way.rnrnFirst and most important question set:rnWhat should I do with any walls? I understand there are a lot of different approaches (bouncing back, inamuro, free slip, no slip, complex things, …) – but I fail programming any of these. As far as I understand, for a simple pipe flow I need a bouncing back condition.rnrnIs this still right? rn>>Yes, thats right. Have a look at our example code.rnrnIf so, all I have to do is to take the distribution functions pointing towards the wall (e.g. pointing North, Northeast, Northwest) and put them into the wall (South, Southeast, Southwest). [This ought to be free slip or what it is called.] Now, if I switch east and west I should have no-slip.rnrnIs this still right? rn>>Yes, thats right again. You may have a look in the standard literature, e.g. Sukop’s book “”Lattice Boltzmann Modelling””.rnrnAnd then, what do I do if an obstacle is to be simulated? There could be corners of which I have absolutely no clue what to do with them.rn>> You can also use bounce back or an interpolation sheme like those of Bouzidi. Have also a look at our 3d example “”cylinder3d”” where we use the later one.rnrnrnTo the not critical questions:rnrnIs there any way to set boundary conditions by defining macroscopic parameters (e.g. von Neumann, Dirichlet)? rn>> Yes, there are may scheme. You may have a look in the standard literature, e.g. Sukop’s book “”Lattice Boltzmann Modelling””. rnrnrnIs there a way, to realize different viscosities? I think, viscosity is only used in the collision, but can I just use different (and chaning) viscosities in a single cell (and keep conservation of mass)?rn>> You can set it different for any cell for the collision step. However, it may not make sence physically.rnrnMany thanks for your time and answers.January 20, 2014 at 4:14 pm #2134mathiasKeymasterSee the quotes.rnMathias
-
AuthorPosts
- You must be logged in to reply to this topic.