Force calculation on a voxelised object

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Hi all, I have just come across the code FluidX3d and am attracted by its efficient calculations. I'm now having some problems using it to perform a process where an object is entering the water at a constant velocity U, so I'm looking for some help here:
I used read_stl() with lbm.voxelize_mesh_on_device() to read the object into the LBM Domain for voxelisation, and then used mesh->translate(U) to achieve its translational motion, but when I wanted to use lbm.calculate_force_on_object (TYPE_S) to calculate the force on the object during its entry into the water but it fails, the force on the object is always 0 during the whole simulation, now I'm not sure if this way I can get the force on the object or if I have a mistake in understanding or doing it?