Wierdly behaving 3D objects / Meshes

[MGRAFF2006]

I am pretty much a noob at fluid dynamics, but need to do some quick calculations on the characteristics of some boats for digital prototyping.

After some poking around I started to get a hang of FluidX3D and decided instead of just changing values, reading the docs and understanding the setup.cpp i would try to create my version of one of the scenarios.

In this case i took the f1 car simulation and tried to get one of our Dummy Models in. Which didn't really ended up working:

Here is a picture of the original 3D Model in Autodesk Fusion:

I know it is probably not recommended having models with multiple non connected parts, but this is the version i have at the moment, also tried other variants (different models in different simulations to try to debug it myself) which I unfortunately don't have anymore.

But a resume of my tests could be, that many of the models i tested were having weird shapes like that, and some would change their shapes while the simulation is running even though i set them as Solid.

Really don't know what is wrong / what i should try anymore. Thanks for any Help / Hint in advance

Here you can find the .stl file and my setup.cpp: issue.zip

[gitcnd]

Loads OK for me - you probably need a larger simulation? Try 14000u instead of 4000u

I ran it like this from WSL:-

/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe start "cmd.exe '/c mode con: lines=80 & bin\FluidX3D.exe -f ..\..\cat.stl -r 16000 --SUBGRID --rotz 90 --rotx 180 --roty 180 --try -0.9 -y 1 -z 0.5 -x 0.3 -c 0.15 --aoa 0.0 --slomo 200.0 --fps 60 --SRT --UPDATE_FIELDS --GRAPHICS --EQUILIBRIUM_BOUNDARIES --FP16S --D3Q15 & pause'"

using my branch from here: https://github.com/gitcnd/FluidX3D/tree/inline_things

What are the "some quick calculations on the characteristics" you're trying to work out?

For context - I'm the author of the free Fusion360 "Airfoil Tools" add-in - which might also be able to help.

[ProjectPhysX]

Hi @MGRAFF2006,

I'm sorry that the first thing you see is something not working. Let's get to the bottom of it. Thanks for already providing the reproducer! I need some more information: What hardware are you running this on? Maybe it is an issue with the particular drivers.

Running this exact reproducer on my system (tested on 3 OpenCL devices: Arc A750, UHD 630 and i7-8700K), the setup looks fine and I can't observe the artifacting. The mesh looks also fine.

To place the model in the center, use this:

    Mesh* cat = read_stl(get_exe_path()+"../stl/cat.stl");
    cat->rotate(float3x3(float3(0, 0, 1), radians(-90.0f))); // rotate -90 degrees around z-axis
    const float scale = 0.8f*fmin(fmin(lbm_N.x/cat->get_bounding_box_size().x, lbm_N.y/cat->get_bounding_box_size().y), lbm_N.z/cat->get_bounding_box_size().z); // scale parts
    cat->scale(scale);
    const float3 offset = lbm.center()-cat->get_bounding_box_center();
    cat->translate(offset);
    cat->set_center(cat->get_bounding_box_center()); // set center of meshes to their bounding box center
    lbm.voxelize_mesh_on_device(cat);

Kind regards, Moritz