boundary condition

[amirhosseinrezaei9776]

Dear Yihao-Shi,

I recently came across your impressive work with GeoTaichi, and I wanted to express my admiration for your contributions to the field.

I have been experimenting with your code and created a simple example based on the column collapse scenario, with some parameter modifications. However, I encountered the following error during my simulation:

RuntimeError: Error:: /max_velocity_constraint/ is set as zero!

I would greatly appreciate any guidance or assistance you could provide to help me resolve this issue. Thank you in advance.
here is the fully code:

`from geotaichi import *

init(device_memory_GB=4)

mpm = MPM()

mpm.set_configuration(domain=ti.Vector([20., 20., 20.]),
dimension="3-Dimension",
background_damping=0.02,
gravity=ti.Vector([0., 0., -9.8]),
alphaPIC=0.005,
mapping="USF",
stabilize=None,
shape_function="GIMP",
material_type="Solid")

mpm.set_solver(solver={
"Timestep": 0.1,
"SimulationTime": 5.,
"SaveInterval": 0.1
})

mpm.memory_allocate(memory={
"max_material_number": 1,
"max_particle_number": 1.0e5
})

mpm.add_material(model="MohrCoulomb",
material={
"MaterialID": 1,
"Density": 1700.0,
"YoungModulus": 10e5,
"Cohesion": 1000.,
"Friction": 28.
})

mpm.add_element(element={
"ElementType": "R8N3D",
"ElementSize": ti.Vector([0.5, 0.5, 0.5]),
"Contact": {
"ContactDetection": False
}
})

mpm.add_region(region=[{
"Name": "region1",
"Type": "Rectangle",
"BoundingBoxPoint": ti.Vector([1., 1., 1.]),
"BoundingBoxSize": ti.Vector([10., 10., 10.]),
"zdirection": ti.Vector([0., 0., 1.])
}])

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

mpm.add_boundary_condition(boundary=[
{
"BoundaryType": "VelocityConstraint",
"Velocity": [0., 0., 0.],
"StartPoint": [0., 0., 0.],
"EndPoint": [20., 20., 1.]
},

                                    {    
                                         "BoundaryType":   "VelocityConstraint",
                                         "Velocity":       [0., 0., 0.],
                                         "StartPoint":     [0., 0., 0.],
                                         "EndPoint":       [1., 20., 20.]
                                    },

                                    {
                                         "BoundaryType":   "VelocityConstraint",
                                         "StartPoint":     [0., 0., 0.],
                                         "EndPoint":       [20., 1., 20.],
                                         "Velocity":       [None, 0., None]
                                    },

                                    {
                                         "BoundaryType":   "VelocityConstraint",
                                         "StartPoint":     [0., 0.5, 0.],
                                         "EndPoint":       [20., 1., 20.],
                                         "Velocity":       [None, 0., None]
                                    }
                                ])

mpm.select_save_data()

mpm.run()
mpm.postprocessing()`

[Yihao-Shi]

You should define max_velocity_constraint in the 'memory' dictionary,

mpm.memory_allocate(memory={
"max_material_number": 1,
"max_particle_number": 1.0e5
})

please see DPmaterial for more details.