Since its introduction, Automatic Mesh Sizing has greatly simplified the modeling process. Automatic Mesh Sizing defines a mesh that is optimized for the model and accurately represents every detail of the geometry.
A good representation of the geometry is only one requirement for a high fidelity solution. For example, the flow on a simple model with a uniform mesh can contain significant gradients. The results on the coarse mesh may not be highly accurate, but they do indicate flow trends. These trends can be used to identify where the elements should be concentrated to improve solution accuracy.
Mesh Adaptation uses solution results to progressively improve the mesh definition. The simulation is run several times. Each time the results in the previous cycle are used to improve the mesh in the next cycle. The result is a mesh that is optimized for the particular simulation. The mesh is finer for high gradient regions, and coarser elsewhere.
When Mesh Adaptation is enabled, the following occurs:
The result is an intelligently refined mesh that is tuned for the flow and temperature results fields.
Using Mesh Adaptation
To enable Adaptation, open the Solve dialog, and click the Adaptation tab.
The Adaptation dialog contains several Mesh Adaptation controls. The following items are the most commonly used. They define essential behavior including the number of adaptive cycles and if the results from intermediate cycles are saved:
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Enable Adaptation |
To enable Mesh Adaptation, check Enable Adaptation. |
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Cycles to Run |
By default, three adaptation cycles are run. To run a different number, change Cycles to Run. Note that the total number of scenarios includes a baseline plus the specified number of cycles. If Adaptation is enabled before running a simulation, an initial baseline is run in addition to the specified number of cycles:
Total cycles = Cycles to Run + 1
If Adaptation is enabled after running a simulation, only the prescribed number of Cycles to Run are run. The existing scenario is used as the baseline. |
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Save Cycles |
To save each intermediate mesh, enable Save Cycles. Each time a scenario finishes, it is automatically cloned, and the cycle number is appended to the base scenario name. For example:
Note: Throughout the process, Scenario 1 is always the active scenario. At the end, Scenario 1 contains the final mesh. The intermediate meshes are contained in the scenarios with "Mesh" appended to their names.
Because each mesh cycle is saved to a unique scenario, it is easy to use the Design Review Center and the Decision Center to study the effect of mesh sensitivity and to determine mesh dependency. If Save Cycles is disabled, only the final mesh and results are saved in the design study. The intermediate adaptation cycles are discarded. |
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Allow Coarsening |
By default, Mesh Adaptation only refines the mesh. To allow it to make the mesh coarser (thus preventing the mesh from growing too large), enable Allow Coarsening. |
Mesh Adaptation does not support the following simulation types or settings:
When using Mesh Adaptation, it is important to know when the solution has achieved mesh independence. Mesh independence is the coarsest mesh that produces results that do not change after the mesh is refined. During each adaptation step, Simulation CFD evaluates the pressure, velocity, and temperature fields to determine how close your solution is to mesh independence. At the conclusion of each step, Simulation CFD reports the mesh independence status in the Output bar in a message similar this:
Mesh independence: Pressure: 85% Velocity 98% Temperature 97%
These values indicate how converged your simulation is for each quantity. Higher values indicate less sensitivity to the mesh, which means your solution is approaching mesh independence.
For best results, you should ensure that each adaptation cycle runs to convergence (or as close as possible). If your adaptation cycles only run for a small number of iterations, this failing to reach convergence, the Mesh Independence indicators will not be accurate.