====== Wind Field Diastrophy ======
The purpose of the Wind Field Diastrophy is to progress slowly from an undisturbed flow in the model area to a flow around the structure. 

To obtain this the buildings are made "solid" in 3 steps: 
In the first step (100%), the wind speed at the facades equals the free flow velocity, 
in the second (50%) it is half the free stream velocity 
and in the final step (0%) the wind speed is zero at the building walls which is the normal condition.

===== Possible Problems & Solution =====

==== High divergence after diastrophy ====

If the model are is very complex, the model might have troubles to solve the wind field. 

Possible solutions: Small modifications in the model, increase the border grids or increase the model height.

See also [[kb:flow|Knowledge Base 10: Flow Problems]]