r""" Gmsh2OPS: Case 1 ================= This example demonstrates how to read a GMSH model by dimension and entity IDs and convert it to an OpenSeesPy model using the `Gmsh2OPS` class from the `opstool` library. """ # %% # This case primarily uses the ``dimension`` and ``entity`` ID information from ``GMSH`` to convert the model into an OpenSees format. # Refer to the dimensions and entity IDs in `Elementary entities vs. physical groups `_. import gmsh import openseespy.opensees as ops import opstool as opst # %% # GMSH model creation and mesh generation # ----------------------------------------- # `t1: Geometry basics, elementary entities, physical groups `_ gmsh.initialize() # Initialize # Create rectangles with entity tags 1 and 2, the function returns entity IDs rect1 = gmsh.model.occ.addRectangle(x=0, y=0, z=0, dx=2, dy=3, tag=1) rect2 = gmsh.model.occ.addRectangle(x=2, y=0, z=0, dx=2, dy=3, tag=2) # Remove duplicate entities, ensuring overlapping edges between the two rectangles are kept as one gmsh.model.occ.removeAllDuplicates() # Synchronize the current Gmsh model, this step is mandatory gmsh.model.occ.synchronize() # Get the boundary lines of the two rectangles; dimTags identifies the dimension and entity lines1 = gmsh.model.getBoundary(dimTags=[(2, rect1)], oriented=False) lines2 = gmsh.model.getBoundary(dimTags=[(2, rect2)], oriented=False) # Set mesh division seeds: constrain each boundary line of the rectangles to generate 21 nodes # Since curves are inherently 1D, only entity IDs are required without specifying dimensions for l in lines1: gmsh.model.mesh.setTransfiniteCurve(tag=l[1], numNodes=21) for l in lines2: gmsh.model.mesh.setTransfiniteCurve(tag=l[1], numNodes=21) # Constrain mesh generation for the plane as well to ensure internal regularity # Planes are inherently 2D, so only entity IDs are needed gmsh.model.mesh.setTransfiniteSurface(tag=rect1) gmsh.model.mesh.setTransfiniteSurface(tag=rect2) # Set mesh algorithm, enable RecombineAll (1 for enabling), merging triangular meshes into quadrilateral ones gmsh.option.setNumber("Mesh.RecombineAll", 1) gmsh.option.setNumber("Mesh.RecombinationAlgorithm", 1) # Generate the mesh; since it's for surfaces, dim=2 gmsh.model.mesh.generate(dim=2) # By default, GMSH generates first-order elements; change the mesh on surface 2 to second-order (nine-node quadrilaterals) # First, hide surface 1 by setting its visibility to 0 gmsh.option.setNumber("Mesh.MeshOnlyVisible", 1) gmsh.model.setVisibility(dimTags=[(2, 1)], value=0, recursive=True) # Then, set the mesh order for all currently visible objects to 2 gmsh.model.mesh.setOrder(2) # Reactivate surface 1 gmsh.model.setVisibility(dimTags=[(2, 1)], value=1, recursive=True) # Write the mesh to a file # gmsh.write("t1.msh") # Launch the GUI for visualization # gmsh.fltk.run() # %% # GMSH to OpenSees conversion # --------------------------------- ops.wipe() # Initialize a basic 3D model with 6 degrees of freedom per node ops.model("basic", "-ndm", 3, "-ndf", 6) # Define an elastic isotropic material # Material ID: 1 # Elastic modulus: 2e8 # Poisson's ratio: 0.3 # Density: 7.85 ops.nDMaterial("ElasticIsotropic", 1, 2e8, 0.3, 7.85) # Define a section using PlateFiber # Section tag: 1 # Material tag: 1 (linked to the material defined above) # Thickness: 0.005 secTag = 1 ops.section("PlateFiber", secTag, 1, 0.005) # %% # Initialize GMSH to OpenSeesPy converter with 3D model and 6 degrees of freedom per node GMSH2OPS = opst.pre.Gmsh2OPS(ndm=3, ndf=6) # Read the saved .msh file generated by GMSH # GMSH2OPS.read_gmsh_file("t1.msh") GMSH2OPS.read_gmsh_data() # Read directly from the current GMSH model in memory # Finalize and close gmsh.finalize() # Create OpenSeesPy node commands based on all nodes defined in the GMSH file GMSH2OPS.create_node_cmds() # Create OpenSeesPy element commands for specific entities # ShellMITC4 elements (4-node shell elements) ele_tags_n4 = GMSH2OPS.create_element_cmds( ops_ele_type="ShellMITC4", # OpenSeesPy element type ops_ele_args=[secTag], # Additional arguments for the element (e.g., section tag) dim_entity_tags=[(2, 1)], # Dimension-entity tags to specify which elements to create ) # ShellMITC9 elements (9-node shell elements) ele_tags_n9 = GMSH2OPS.create_element_cmds( ops_ele_type="ShellMITC9", # OpenSeesPy element type for 9-node shells ops_ele_args=[secTag], # Additional arguments for the element (e.g., section tag) dim_entity_tags=[(2, 2)], # Dimension-entity tags to specify which elements to create ) # Done! # %% # Define boundary conditions # Get the boundary dimension tags for the two surfaces boundary_dim_tags = GMSH2OPS.get_boundary_dim_tags([(2, 1), (2, 2)]) # Remove the shared boundary between the two surfaces boundary_dim_tags.remove((1, 2)) # Print the remaining boundary dimension tags print("Boundary dim_tags:", boundary_dim_tags) # Create fix commands for the boundary with constraints applied to all 6 degrees of freedom (DOFs) fix_node_tags = GMSH2OPS.create_fix_cmds(dim_entity_tags=boundary_dim_tags, dofs=[1] * 6) # %% opst.vis.pyvista.set_plot_props(point_size=0, mesh_opacity=0.75, cmap_model="viridis") plotter = opst.vis.pyvista.plot_model() plotter.show() # %% # sphinx_gallery_thumbnail_number = 2 opst.vis.pyvista.set_plot_props(show_mesh_edges=False) plotter = opst.vis.pyvista.plot_eigen([1, 9], subplots=True) plotter.show()