Initial gravity field

[Yihao-Shi]

Currently, the code can only compute the initial gravity field accurately for rectangular initial geometries. For arbitrarily shaped material points, the calculation may be incorrect due to the simplicity of the embedded algorithm.

To achieve accurate gravity field computation for arbitrary shapes, you can manually input the distance of each material point from its free surface as a numpy array and assign it using the GravityField keyword, as shown below:

mpm.add_body(body={
                       "Template": {
                                       "RegionName":         "region1",
                                       "nParticlesPerCell":  2,
                                       "BodyID":             0,
                                       "MaterialID":         1,
                                       "ParticleStress": {
                                                              "GravityField":     /**your_input_array**/,
                                                              "InternalStress":   ti.Vector([-0., -0., -0., 0., 0., 0.]),
                                                              "Traction":         {}
                                                         },
                                       "InitialVelocity":ti.Vector([0, 0, 0]),
                                       "FixVelocity":    ["Free", "Free", "Free"]    
                                       
                                   }
                   })