Applying different densities to a fuselage

[Jules Galzin]

Hello,

I have designed a fuselage on Open VSP. This fuselage is made up of three different materials. It is divided into three areas (nose, canopy, and the rest of the fuselage), which I have designed using subsurfaces. I would like to know if it is possible to assign a different density to each of these areas. I have the impression that I can only specify one density that applies to the entire fuselage. If it is possible to assign different densities to the areas of my fuselage, could you please help me? 

Thank you in advance. 

Jules GALZIN

[Brandon Litherland]

There isn't a method of directly setting different surface densities that I can recall.  As is, your internal volume density is set to 1.0 which will have a significant effect on your analysis. I suppose if you wanted to try and work around the problem, you could set the volume density to 0, and use negative volume geoms to cut the surface and then analyze each section in isolation.  That would be a mess, however, and I don't really recommend it. I suppose it would depend on how different the materials are in those regions and how much that difference matters when you consider the weight of the fuselage structure, etc.  If the mass or CG location is only changing by one inch, for example, the pilot shifting around could alter it more than that.

[Rob McDonald]

The MassProp calculation in OpenVSP does not use SubSurfaces.  However, version 3.45.2 will report subsurface breakdowns of surface area from CompGeom.

It won't get you center of mass or inertias, but it will give you the areas of the canopy and nose -- and you can work from that.

Otherwise, you could build up the model in the FEA Structure capability.  There you can use subsurfaces to assign material properties to different parts.  However, FEA Structures only works on one component at a time.

Rob