[Rukiye]

Hi everyone!

I am simulating airflow around buildings. My domain is quite large (2800mx2800mx400m) and I think the distance between the end of the last building and pressure outlet is acceptable (~600m) since the blockage ratio is about 3% where the heighest building is 65m and the rest are in a range of 18-26m. I am using realizable k-e model with standard wall functions. Residuals: for x,y,z velocity is 10^-7; k and e 10^-6 and for continuity 10^-5.

1- My problem is; even if I reduced the under relaxation factors, I keep receiving that reverse flow and my simulation doesn't converge.

I change several times the mesh (coarser and finer mesh) and kept reducing the max skewness (last 94%). Actually I am not quite sure how to pursue a grid sensitivity analysis, but the mesh seems fine.

2- I would like also to implement sang grain roughness height (ks) and roughness constant (Cs) values according to this study: [Blocken 2007] http://sts.bwk.tue.nl/Blocken/pdf/Pr...simulation.pdf

Fleunt doesn't allow an input larger than 1, for roughness height. Is there anyway to change it?

I appreciate very much any kind of input