Hi @sholz,
Sorry for the late reply! Very busy these few weeks.
With regards to this simulation, meshing is highly critical when it comes to urban flow simulations. I previously did some work with a relatively dense and complex urban environment. You can refer to the post and this as well for some insight, but lets take a look at what we can do for yours. Also do refer to this project here where you can observe the meshing setup.
For starters, checking the mesh directly on SimScale is not very ideal as you have no idea on the mesh parametrics or how the mesh actually looks like as there are some limitations. As you already have paraview, you can check the surfaces and area meshes through there directly which would give you a better interpretation of how the mesh is like. For detailed parametrics such as orthogonal quality and all that, its a little more complex to get so let me know if you need it or not.
Looking at your mesh , you need to add additional surface refinement to the individual building surfaces and the floor. It is much to corase and there are irregular mesh cells that are identical to the issue I faced in the previously stated posts. Lets get the surface and overall meshes fixed first before moving on to the surrounding mesh.
Cheers.
Regards,
Barry