Boundary condition for an open end

[vivon]

Hi, I am trying to simulate Rayleigh Benard convection in a 3D box. I am able to run the code provided in examples. However, I would like to have a boundary similar to a tea cup open to atmosphere at the top instead of no-slip. I have tried using pressure boundary at top, but the simulation fails (-nan values). Any help or hints will be greatly appreciated, thank you in advance.

[robin.trunk]

Hi,rnrnto allow a free outflow, the ConvectionBoundary can be used. It exists for the fluid and the temperature as well, simply replace the boundary condition for material number 3, for the fluid byrn NSboundaryCondition.addConvectionBoundary(superGeometry, 3, NSomega);rnand for the temperature byrn TboundaryCondition.addConvectionBoundary(superGeometry, 3);rnrnbestrnrobin

[vivon]

Thank you, Robin.rnrn I wasn’t aware that such a boundary existed in OpenLB. I used TboundaryCondition.addConvectionBoundary(superGeometry, 3, Tomega); instead of what you suggested due to incorrect number of arguments.rnrnBut for some reason , I am receiving a “”segmentation fault (core dumped)”” error. I have checked the memory usage it seems fine. Any suggestions? Thanks in advance

[robin.trunk]

Hi,rndid you modify the thermal3D example or did you start your own code?rnThe function addConvectionBoundary for the fluid expects three arguments, while the one for the temperature just expects two. So I assume the wrong function is called. This would explain the segmentation fault.rnIs TboundaryCondition initialized with a AdvectionDiffusion Descriptor as template and the SuperLattice in the arguement also?rnrnbestrnRobin

[vivon]

Sorry for the delay. I was trying to implement what you said in thermal3D code of openLB 0.9 and it failed. But in the latest version 1.0, it works properly. Thank you so much for the help. rnrnIs there any options in the forum to mark your suggestion as the answer? rnThanks again Robin, you saved a lot of time for me.

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