B-b-v: 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 structures.
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 Knowledge Base 10: Flow Problems