How do I find the time varying center of gravity location of my deforming body using DPF?

Vishnu

The COG of a body might vary with time as the body deforms and you might be interested in knowing how to compute the time varying COG.

This example also highlights on how you can create your own mesh with DPF.

Vishnu

Use the below function like :

find_COG_at_time('MYBODY',3) #Please remember to create a body named selection on the one you are interested in knowing the COG

def find_COG_at_time(bodynamedselection,timepoint):
     import mech_dpf
     import Ans.DataProcessing as dpf
     #Result Data
     analysis1 = ExtAPI.DataModel.Project.Model.Analyses[0]
     dataSource = dpf.DataSources(analysis1.Solution.ResultFilePath)
     #Get mesh
     my_model = dpf.Model(analysis1.Solution.ResultFilePath)
     my_mesh = my_model.Mesh
     #mytime
     my_time_scoping = timepoint
     #Get Deformation
     u = dpf.operators.result.displacement(time_scoping=my_time_scoping,data_sources=dataSource)
     disp_field = u.outputs.fields_container.GetData()[0]
     #Create my own mesh
     created_mesh=dpf.MeshedRegion(my_mesh.Nodes.Count,0)
     for node in my_mesh.Nodes:
         created_mesh.AddNode(node.Id,[node.X+disp_field.GetEntityDataById(node.Id)[0],node.Y+disp_field.GetEntityDataById(node.Id)[1],node.Z+disp_field.GetEntityDataById(node.Id)[2]])
     createdmesh_nodeids = created_mesh.NodeIds
     for elem in my_mesh.Elements:
         created_mesh.AddSolidElement(elem.Id,map(lambda x: createdmesh_nodeids.IndexOf(x), elem.CornerNodeIds))
     #scoping operator    ns_op=dpf.operators.scoping.on_named_selection(requested_location='Elemental',named_selection_name=bodynamedselection,data_sources=dataSource)
     mymeshscoping = ns_op.outputs.mesh_scoping
     #Volume field
     cogfield = dpf.operators.geo.center_of_gravity(mesh = created_mesh,mesh_scoping=mymeshscoping).outputs.field
     #COG
     return list(cogfield.GetData().Data)

Paul Profizi

Hi @Vishnu, thank you for this example!

One remark though:

This is tagged as "PyDPF", yet as it is using the API for use within Mechanical, I am afraid this will create confusion for people trying to use this with PyDPF-Core/Post. Is there a better suited tag available? Or maybe we should create one specific for use of DPF from within Mechanical, be it in Python.

Vishnu

I think so too we may need to create one for DPF from within Mechanical

James Derrick

Hey! I added the DPF tag to your post! Also can you confirm that COG = "Centre of Gravity"? I don't think you state it anywhere.