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ANSYS MESHING – Multizone + Inflation + Face Meshing

Source: ANSYS HELP

The MultiZone mesh method provides automatic decomposition of geometry into mapped (structured/sweepable) regions and free (unstructured) regions. It automatically generates a pure hexahedral mesh where possible and then fills the more difficult to capture regions with unstructured mesh. The MultiZone mesh method and the Sweep mesh method operate similarly; however, MultiZone has capabilities that make it more suitable for a class of problems for which the Sweep method would not work without extensive geometry decomposition.

MultiZone Meshing

Inflation

The Inflation Option settings determine the heights of the inflation layers. The following options are available:

  • Smooth Transition – This is the default. The Smooth Transition option uses the local tetrahedral element size to compute each local initial height and total height so that the rate of volume change is smooth. Each triangle that is being inflated will have an initial height that is computed with respect to its area, averaged at the nodes. This means that for a uniform mesh, the initial heights will be roughly the same, while for a varying mesh, the initial heights will vary.The computations used for prism layer growth are as follows:
    • The following value is computed at each node on the prism base:Height of last prism (H) = Transition_Ratio * average_edge_length
    • The height of the first layer (h) is computed using the following formula, where g = Growth Rate and n = Number of Layers:H = h * (g ^ (n-1))Increasing the value of the Growth Rate control reduces the total height of the inflation layer. The total height approaches an asymptotic value with respect to the number of inflation layers.For details about the additional controls that appear when Smooth Transition is selected, refer to the descriptions of the Transition RatioMaximum Layers, and Growth Rate controls.Note:  The Smooth Transition option works differently for the MultiZone mesh method. See MultiZone Support for Inflation for details.
  • Total Thickness – The Total Thickness option creates constant inflation layers using the values of the Number of Layers and Growth Rate controls to obtain a total thickness as defined by the value of the Maximum Thickness control. Unlike inflation with the Smooth Transition option, with the Total Thickness option the thickness of the first inflation layer and each following layer is constant.For details about the additional controls that appear when Total Thickness is selected, refer to the descriptions of the Number of LayersGrowth Rate, and Maximum Thickness controls.
  • First Layer Thickness – The First Layer Thickness option creates constant inflation layers using the values of the First Layer HeightMaximum Layers, and Growth Rate controls to generate the inflation mesh. Unlike inflation with the Smooth Transition option, with the First Layer Thickness option the thickness of the first inflation layer and each following layer is constant.For details about the additional controls that appear when First Layer Thickness is selected, refer to the descriptions of the First Layer HeightMaximum Layers, and Growth Rate controls.
  • First Aspect Ratio – The First Aspect Ratio option creates inflation layers using the values of the First Aspect RatioMaximum Layers, and Growth Rate controls to generate the inflation mesh.Post inflation is not supported when Inflation Option is First Aspect Ratio.For details about the additional controls that appear when First Aspect Ratio is selected, refer to the descriptions of the First Aspect RatioMaximum Layers, and Growth Rate controls.
  • Last Aspect Ratio – The Last Aspect Ratio option creates inflation layers using the values of the First Layer HeightMaximum Layers, and Aspect Ratio (Base/Height) controls to generate the inflation mesh.Figure 60: Last Aspect Ratio Option illustrates this option. With the Last Aspect Ratio method, the First Layer Height is specified. The offset height for the last layer is calculated from the local base mesh size and specified Aspect Ratio (base/height). For example, if you specify a value of 3 for Aspect Ratio (base/height), the offset height of the last layer will be the local base mesh size divided by 3. The local growth rate is calculated using Maximum layers to create exponential growth through the intermediate layers.Figure 60: Last Aspect Ratio Option.

Face Meshing Control

Face meshing controls enable you to generate a free or mapped mesh on selected faces. The Meshing application determines a suitable number of divisions for the edges on the boundary face automatically. If you specify the number of divisions on the edge with a Sizing control, the Meshing application attempts to enforce those divisions.

To set the Face Meshing controls, highlight Mesh in the Tree Outline, and right-click to view the menu. Select Insert> Face Meshing. You can also click Mesh in the Tree Outline, and select the Mesh Control Context Toolbar, then select Face Meshing from the drop-down menu.

Definition>Mapping is set to Yes by default, also exposing Constrain Boundary and Advanced settings. If Mapping is set to No, the Mesher will perform a free mesh and the Constrain Boundary and Advanced settings are not available.

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