Keep the model as neat and as simple as possible.

Make sure the buildings sit firmly on the ground to avoid small gaps.

If exporting as a SAT file fails an alternative is to export a 3D model as an obj file.

Create a new design study within CFD and select the obj file.

An external volume can be used to set the air volume

Click on the six max and min snap buttons to set the size of the air volume

Generate wrap will create a smoothed surface over the model, this avoids sharp corners that can cause the meshing process to fail.

Transfer the wrap to the setup.

Right click on the air volume and from the edit option set the type to fluid and name to air.

Also from the right click menu select outline mode.

Then right click on the buildings and set the type to solid and name to brick or concrete.

From boundary conditions right click on a surface to set the velocity.

On the opposite surface set the pressure to zero.

Click solve and choose CLOUD for the solver computer.

The solver status is available from the Windows bar.

Many of the sharp corners have been smoothed in the image above.

Right click on the air and set to transparent or outline.

Choose planes or traces as the result type, each can be moved and rotated as required

By dragging the arrows or the angles.

A variety of display types can be shown at the same time by clicking on the icons and then adding a plane or seed.

Right click on the results to hide, remove or edit.

If Solve still fails, try scaling your model at 1:10 or 1:100, don't forget velocity is affected.

Similitude of speed(V): In agreement with Froude's law, the velocity scale is the square root of the length scale, so:

Scaling a site at 1:100 for CFD

S(V) = S1/2(L) = sqrt(100) = 10 (times slower than in real life)

Velocity is 1/10 of actual @ 1:100

Velocity is 1/sqroot(10) = 1/3.162 of actual @ 1:10.