Stokes’ flow elements neglect acceleration, and thus requires no additional stabilization.
Standard 6 node triangular element for stokes flow, with quadratic geometry, velocity and linear pressure. Both compressible and incompressible material behavior is supported (and also the seamless transition between the two). The element features are summarized in Table 40.
| Keyword | Tr121Stokes |
| Description | Standard 6 node triangular element for stokes flow, with quadratic geometry, velocity and linear pressure |
| Specific parameters | - |
| Unknowns | Unknown pressure in nodes 1–3 with unknown velocity (V_u and V_v) in all 6 nodes. |
| Approximation | Quadratic approximation of geometry and velocity, linear pressure approximation. |
| Integration |
|
| Features | - |
| Status | Reliable |
Standard 10 node tetrahedral element for stokes flow, with quadratic geometry, velocity and linear pressure. The element features are summarized in Table 41.
| Keyword | Tet21Stokes |
| Description | Standard 10 node tetrahedral element for stokes flow, with quadratic geometry, velocity and linear pressure |
| Specific parameters | - |
| Unknowns | Unknown pressure (P_f) in nodes 1–4, and unknown velocity (V_u, V_v, V_w) in all nodes. |
| Approximation | Quadratic approximation of geometry and velocity, linear pressure approximation. |
| Integration |
|
| Features | - |
| Status | Untested |
So called “Mini” element in 2D. A 3 node triangular element for stokes flow, with linear geometry and pressure. Velocity is enriched by a bubble function. Should not be used with materials that have memory (which is uncommon for flow problems). The element features are summarized in Table 42.
| Keyword | Tr1BubbleStokes |
| Description | So called “Mini” 2D element |
| Specific parameters | - |
| Unknowns | Unknown pressure (P_f) in all nodes, and unknown velocity (V_u, V_v) in all nodes and one internal dof manager. |
| Approximation | Linear geometry and pressure. Velocity is enriched by a bubble function. |
| Integration |
|
| Features | - |
| Status | Untested |
So called “Mini” element in 3D. A 4 node tetrahedral element for stokes flow, with linear geometry and pressure. Velocity is enriched by a bubble function. Should not be used with materials that have memory (which is uncommon for flow problems). The element features are summarized in Table 43.
| Keyword | Tet1BubbleStokes |
| Description | So called “Mini” 3D element |
| Specific parameters | - |
| Unknowns | Unknown pressure (P_f) in all nodes, and unknown velocity (V_u, V_v) in all nodes and one internal dof manager. |
| Approximation | Linear geometry and pressure. Velocity is enriched by a bubble function. |
| Integration |
|
| Features | - |
| Status | Untested |