一个算例介绍 libmesh 的类

标签： libmesh 类

2014-09-19 12:40 415人阅读评论(0) 收藏举报

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开源 libmesh（8）

算例出处：http://libmesh.sourceforge.net/systems_of_equations_ex1.php

11int main(int argcchar** argv)

13 {

14 LibMeshInit init(argc, argv);

15 Mesh mesh(init.comm());

16 /*libMesh::Mesh

17 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1Mesh.php

18 */

19 MeshTools::Generation::build_square(mesh,

20 15, 15,

21 0., 1.,

22 0., 1.,

23 QUAD9);

24 /*

25 * libMesh::MeshTools:Generation

26 * http://libmesh.sourceforge.net/doxygen/namespacelibMesh_1_1MeshTools_1_1Generation.php

27 * 几何生成函数（点，线，面，块，球）

28 * build_point, build_line, build_square

29 * build_cube, build_sphere

30 * build_extrusion, build_delaunay_square

31 */

33 EquationSystems equation_systems(mesh);

34 /*

35 *libMesh::EquationSystems

*http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1EquationSystems.php

37 * 共有函数：构造／析构， clear(), init(), update, has_system(), get_system()

38 * matrix(); add_system(), delete_system(), n_vars(), n_active_dofs(), solve(), get_solution(), get_mesh(), get_info

39 */

41 LinearImplicitSystem &system = equation_systems.add_system<LinearImplicitSystem> ("Stokes");

42 /*

43 * libMesh::LinearImplicitSystem

44 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1LinearImplicitSystem.php

45 * add_variable(), attach_assemble_function()

46 */

48 system.add_variable("u",SECOND);

52 system.attach_assemble_function(assemble_stokes);

54 equation_systems.init();

56 equation_systems.parameters.set<unsignedint>("linear solver maximum iterations") =250;

58 equation_systems.get_system("Stokes").solve();

59 }

61 void assemble_stokes(EquationSystems& es,const std::string& system_name)

62 {

63 const MeshBase& mesh = es.get_mesh();

64 const unsigned int dim=mesh.mesh_dimension();

65 LinearImplicitSystem& system=es.get_system<LinearImplicitSystem>("Stokes");

66 const unsigned int u_var = system.variable_number("u");

FEType fe_vel_type = system.variable_type(u_var);

69 FEType fe_pres_type = system.variable_type(p_var);

70 /*libMesh::FEType

71 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1FEType.php

72 */

74 /*libMesh::FEGeneraicBase

75 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1FEGenericBase.php

76 * 函数：get_phi(), get_dphi(), attach_quadrature_rule(); build(); reinit(); get_xyz(); get_JxW(); get_tangents();get_type(); n_shape_functions(); print_info()

77 */

79 /*libMesh::AutoPtr

80 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1AutoPtr.php#details

81 * std::AutoPtr, an AutoPtr owns the object it holds a pointer to, copying an AutoPtr copies the pointer and transfers owners hip to the destination

82 */

83 AutoPtr<FEBase> fe_pres(FEBase::build(dim,fe_pres_type));

85 QGauss qrule(dim, fe_vel_type.default_quadrature_order());

87 fe_vel->attach_quadrature_rule(&qrule);

88 fe_pres->attach_quadrature_rule(&qrule);

90 /* libMesh::DofMap

91 * http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1DofMap.php

92 * 函数：variable_type(), n_dofs()

93 */

94 const DofMap& dof_map = system.get_dof_map();

结尾

libmesh内容非常庞大，相比oofem，可以大概理解这些类。

libmesh::mesh == oofem::domain -> dof，单元数据管理（底层）

libmesh::equationsystem ＝＝ oofem::engmodel －> 物理问题（映射）到有限元空间（平台）

libmesh::linearimplicitsystem == oofem::linearstatic -> 特定有限元空间数值解（实现层）

其他，smart指针设计，单元迭代器，数值积分类，矩阵计算，自适应网格模块等等。

本文大致介绍下libmesh中经常用到的类，当然还有非常多，瞬态问题，非线性问题等等求解器类都非常丰富，使用中继续学习。后文继续介绍该问题的libmesh（有限元）实现思路。