Refinement region Box - obstructing airflow results

Hello! We have been running wind simulations using the butterfly plugin. We used the outdoor airflow example script with the following parameters:-

a) wind velocity of 3.1 m/s
b) Refinement Level - (1,1)
c) Refinement Mode – 3.0
d) Global Cells - 2000000000
e) No. of iterations in solution – 600

When we used Paraview to extract results we found that A unnatural bounding box (same as refinement region) has formed. The results read the refindment region as a obstrcution that obstructs windflow and effect of surrounding nrighbourhood buildings is not reflected. This result looks incorrect as wind does not flow in such a way.

We have tried running the script without a refinement region but we were not able to get proper mesh for the geometry.We have tried removing surrounding buildings to see if the results would change but remained the same.

Really appreciate any help we can get

Hi @Midori You shoud pose some screenshot of your model and the paraview results.
As I know, refinement region will decrease the wind speed inside it. I suggest you to use XYZ grading to get a bettter blockMeshing. And increase the refinement level to (2,3). You can refer to my previous post

Hi @minggangyin. Thank you for the reply. Here are some screenshots of the paraview results.
For further investigation, I ran the simulation with the same parameters as the previous run except without any surrounding buildings to check if the wind shadow caused the box to form and increased the number of iterations. I visualized the results in paraview and extracted the following images.

Comparison of New(left) and Old(right) results.

The refinement region seems to create an obstruction in the wind path. I shall move ahead as per your suggestion to use XYZ grading.


Hi @Midori It is hard to debug your model from the screenshots .Please upload your grasshopper file for further discussion.