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Exporting STL file to the simulation engine: UNKNOWN MATERIAL NUMBER

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    I want to use an STL file (a simple cylinder) to simulate fluid flow. (My ultimate goal is to learn how to import an STL file taken from a porous medium into OpenLB to simulate fluid flow.)

    I considered the “aorta3d” example as a reference and carefully revised the inflow and outflow data. Howoever, when running, I get this error:
    Unknow material number

    However, after this voxelizing starts and I get “Voxelizing … OK”!!!

    Since the material numbers are unknown, the code stops at the prepare geometry step.

    As I’ve always been using the primitives to create the geometry and this my first time using STL, I’m not sure whether there is something wrong with the STL file or the code. I looked through the User’s guide and could not find anything regarding the requirements of the STL file. I would appreciate if you kindly help me to sort it out.

    Many thanks in advance,
    Kind Regards,


    Dear Mehrdad,

    firstly you can check the console output of the voxelizer:

    [STLmesh] nTriangles=2654; maxDist2=0.000610779
    [STLmesh] minPhysR(StlMesh)=(0.199901,0.0900099,0.0117236); maxPhysR(StlMesh)=(0.243584,0.249987,0.0398131)
    [Octree] radius=0.143744; center=(0.221602,0.169858,0.025628)
    [STLreader] voxelSize=0.0005615; stlSize=0.001
    [STLreader] minPhysR(VoxelMesh)=(0.199984,0.0904058,0.0118712); maxPhysR(VoxelMesh)=(0.24322,0.249872,0.0393847)
    [STLreader] Voxelizing … OK

    Please check for your case, if the min and max dimensions of the stl mesh and the voxel mesh are correct.
    In a further step you can check the Octree of the stlindicator with the call:
    stlreader.writeOctree(); // (output is saved in the tmp floder)

    If the octree is not correct you can try to use other indicate functions (e.g. 1 or 3)

    The prepare geometry step is sequential, so you can check after each renaming procedure the output to test, where the renaming problem occurs.

    Best Marc

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