Order of elements

Definition

Flux provides for the user two types of finite elements: first order elements or second order elements.

Type of element Location of nodes Interpolation function
  Automatic mesh generator Mapped mesh generator  
First order

Linear

(1st order polynomial)
Second order

Quadratic

(2nd order polynomial)

With second order elements, the number of nodes is far larger than with first order ones but accuracy is largely increased.

2D application

For a 2D application, the mesh generation is completed with meshing the faces, and second order face elements are directly generated. Remark: first order mesh is also available (even if not really suggested to users) for all the 2D applications except the axisymmetric domain type.

3D application

In 3D, meshing the volumes leads to first order volume elements.

In several physical configurations, it is possible to solve with first order elements.

Generally, it is better to generate the second order elements.

Generate second order elements (3D)

To generate second order volume elements:

Step Action
1

Activate the command:

  • in the Mesh menu, click on Mesh > Generate second order elements

    or in the Mesh toolbar, click on the icon

→

Elements of second order are generated.

The number of mesh elements is increased.

Come back to first order elements (3D)

To come back to first order volume elements:

Step Action
1

Activate the command:

  • in the Mesh menu, click on Mesh > Generate first order elements
→ Mesh elements are the first order elements.