The Additional Adaptation controls complement the primary options for defining Mesh Adaptation.
To view them, expand Additional Adaptation on the Adaptation tab of the Solve dialog.
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Flow Angularity |
By default, Mesh Adaptation adapts the mesh based on the field variables (velocity, pressure, and temperature). To improve the resolution in areas that contain large amounts of flow separation and/or circulatory flow, enable Flow Angularity. |
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Transient Features |
If your flow has "dynamic" regions such as a flow reattachment or vortex shedding, enable Transient Features. This performs three adaptations per error criteria before continuing to the next (tighter) criteria level. The result is that static flow regions are not over-adapted, and dynamic features are better resolved. Note: The total number of adaptation cycles is 3 times the number of Cycles to Run.
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Y+ Adaptation |
Many turbulent flows, particularly those involving external or aerodynamic flows, are sensitive to the thickness of the boundary elements. The parameter that characterizes this is called "Y+," and is a non-dimensional distance between a wall node and its corresponding neighbor node. This is a component of the Turbulent Law of the Wall. To allow the boundary element thickness to vary with each adaptation cycle, enable Y+ Adaptation. The Mesher evaluates the Y+ value throughout the model, and reduces the boundary element thickness where values are too high. The boundary layer thickness does not change at the end of the first adaptation cycle if the simulation had previously been run with Y+ Adaptation disabled: If you wish to run a preliminary simulation without Adaptation, followed by a series of Adaptation cycles that include Y+ Adaptation, do the following before starting the initial simulation:
Note: This form of adaptation is conceptually similar to Automatic Layer Adaptation enabled with Mesh Enhancement. Unlike Automatic Layer Adaptation, however, Y+ Adaptation updates the boundary element thickness at the end of each adaptation cycle instead of each iteration. These two options should not be enabled simultaneously.
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Max Y+ |
According to the Turbulent Law of the Wall and numerous studies, the ideal range for Y+ is between 35 and 350. The default upper limit for Y+ Adaptation is 300. In some demanding cases, (such as very high-speed aerodynamics) it may be necessary to reduce the Max Y+ to achieve the desired accuracy. |
Related Topics
The following topics describe additional parameters on the Adaptation dialog:
Advanced Mesh Adaptation Parameters
To see the effect of Mesh Adaptation on an industrial valve simulation, click here.