Hello

As the deleterious effects of outlet boundary conditions increase in high Reynolds, one way to prevent these effects is to increase the amplitude of the solving domain and to put outlet boundary conditions further away from the center of the domain. if desired and appropriate results are not obtained, the outflow boundary condition is robust and easy to apply. The only thing needed is updating the propagation values of the boundary with neighboring nodes before the outlet boundary condition.

Regards

Hamed Vaseghnia Hi! Thanks for your answer. I can understand what you are saying. Actually I need the piece of code for outflow as well as upper and lower boundary conditions and treatment of corner nodes as my drag values are getting higher at Re=2100 for flow past a square and I an assuming it due to incorrect b.c Can you tell me the code details or refer me some work in which slip b.c on walls and outflow b.c are implemented at outlet. Moreover, the corner nodes are also treated in a better way so that they could not disturb the results. I will be very grateful to you for this utmost favor.

Best Regards

Ahsan

Muhammad Ahsan Nawaz To simply apply the outflow boundary condition in the right hand side edge, you have to update streaming process at outlet boundary by previous nodes :

f(1,xmax,y)=f(1,xmax-1,y)

and so on for other directions...

However, i suggest you to apply pressure boundary condition in high Re. pay attention to intersections of the non-slip boundary conditions and inlet-outlet boundaries. wrong implementation of the corners and their propagation through the domain might highly affect your results. if you require any further information take a look at :

The Lattice Boltzmann Method: Principles and Practice ISBN: 978-3-319-44647-9