/ALE/GRID/FLOW-TRACKING
Block Format Keyword Mean velocity within ALE mesh is used to determine automatically mesh displacement, mesh deformation, and also mesh rotation. The general idea is to have an ALE mesh acting as a tracking window.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
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/ALE/GRID/FLOW-TRACKING | |||||||||
I_def | scale_def | ||||||||
I_rot | scale_rot |
Definition
Field | Contents | SI Unit Example |
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I_def | Enable deformation flag.
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scale_def | Deformation scale factor. Default = 1.0 (Real) |
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I_rot | Enable rotation flag.
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scale_rot | Rotation scale factor. Default = 1.0 (Real) |
Comments
- The grid velocity is calculated based on the mass-weighted average velocity of the material within the ALE mesh. A common application is modeling ALE impactors, such as ALE birdstrikes.
- For all nodes i, the mesh velocity i, is set as:Where,
- Mass averaged velocity
- Node coordinates
- Center of mass
- Average strain rate tensor
- Average spin tensor
- Average gradient of velocity
- Gradient of velocity
- It is possible to disable mesh deformation and/or mesh rotation. It can also be amplified or reduced using scale factors scale_def and scale_rot.
- It is recommended to define Non-Reflecting Frontier on ALE mesh boundaries (/EBCS/NRF).
- A specific treatment is introduced to amplify mesh deformation to track material that tends to escape the ALE boundaries. Without this treatment, average quantities may not adequately track the main flow when there are large velocity gradient differences.