Butterfly refinement mode problem

#1

Hi.

I have an issue with refinement mode, as I think.) When it is 1 seems that simulation works well, but when I make it for example 2 the results are strange. What can cause such a problem? Can it be caused by the scale of the cell? Seems that the problem arrives when the cell is less than 0.25m.

Thanks in advance.

Velocity_refinement%20mode_1%20or%202_|690x487

#2

It is really hard to say just from the images. @TheodorosGalanos do you have any insight on why this might be happening?

#3

@Ilay_s_p It is generally not a good advice to have large jumps in the sizes of neighbouring cells. This is the reason we kind of moved from the idea of refinement region to that of gradient mesh (you can use the wind tunnel gradient component to get an even better result than what you have with a fraction of total cells).

If I undestand your case correctly this is what happens here. The refinement region at 2 levels is creating a big jump in cell size and that brings you that big jump in gradients. I would either reduce it to one (or use a distance refinement mode) or simply use the wind tunnel gradient componet (although for the case of 1 building it might simply wrap around your geometry).

Kind regards,
Theodore.