I imported a 3d building model using STL format and it looked o.k. in the VR Viewer. I have investigated the model in VR Viewer to make sure the geometry is correct. However, when I run the flow simulation around the building, something weird was observed. The building is a solid and there should be no flow penetrating the building in spite of the flow on the building surface because of cartesian grids. I tried to use a finer mesh but there were still some flows penetrating the building and interestingly the locations of penetration were the same. It seemed the PRPS value of a solid (198) was not fully allocated within the building model. Could anybody tell me why and how to solve the problem? Thank you in advance.

It seems like your STL model is not completely "solid". In the CAD program you are using, all obstacles should be of "solid" type, and the interceptions between different obstacles should be "boolean" joined. This might be difficult when your obstacle is complex. Try also to trangulate the STL model with a denser triangle mesh.

Thomas

Thank you very much, Thomas.

The problems have been solved. I used to convert my CAD drawing with 3D Studio and CADfix but it was not successul because I didn't join the individual buildings as a single object when I was doing my CAD drawing. I just tried to join these buildings with 'Union' instruction in ACAD 2000i into a single 'solid' object and then I export the already joined buildings in STL format in ACAD directly. It was successful when I imported the model into PHOENICS and the solid parts of the buildings were correctly represented by caretsian grids.

Many thanks for your help.