10.6.5. The Layers Object

The Layers object is used to control the individual layer objects. You can access the Layers objects in the object selector.

 

10.6.5.1. Layers Tab

A number of possible operations are available for a layer by clicking it in the list box and then selecting one of the icons on the right of the list box, or by right-clicking the object and then selecting an operation from the shortcut menu.

 
10.6.5.1.1. Defining Intermediate Layers

To ensure that the mesh is adequately guided in the spanwise direction, a mesh might require more layers than just a Hub layer and a Shroud layer. You can set up intermediate layers in different ways, as controlled by the Insertion Mode option:

  • Manual - Uniform

    TurboGrid creates the specified number (Count) of layers and positions them uniformly in the spanwise direction from hub to shroud.

    Existing layers are not preserved when you apply the Manual Uniform option.

  • Automatic - Adaptive (default for the ATM meshing approach; unavailable for the ATM3D meshing approach)

    The Automatic - Adaptive option causes TurboGrid to automatically add the "recommended number of additional Layers" (as displayed in the Layers object editor) upon topology generation. The recommended number might be zero, in which case no new layers are added. Whenever new layers are added, a notification appears in the status bar in the lower-left corner. In this mode you have no control over the number of intermediate layers or the positions of the intermediate layers. Switch to the Manual option (described below) if more control is needed.

    Note:  The recommended number of layers is a recommendation based on blade shape, size of the topology around the blade, proximity of inlet/outlet, and so on. As such the recommendation is not always reliable.

  • Manual (unavailable for the ATM3D meshing approach)

    You can control the number and positioning of intermediate layers.

    Existing layers are preserved when you switch to the Manual option. This enables you to, for example, make adjustments after using the Manual - Uniform option.

    You can add one layer at a time either:

    • wherever TurboGrid chooses (right-click any Layer in the list and select New Layer or click New Layer  ), or

    • "after" (on the Shroud side of) any particular existing layer (right-click a layer in the list and select Insert Layer After).

    You can add the recommended number of layers all at once, letting TurboGrid choose the layer positions (right-click a layer in the list and select Auto Add Layers or click Auto Add Layers  ).

    You can select one or (using Shift or Ctrl) more layers, then delete them (right-click the layer or selection of layers and select Delete Selected Layer(s) or click Delete Selected Layer(s)  ).

    Note:  When the Manual option is applied, new layers are not generated upon topology generation or 3D mesh generation. If you want TurboGrid to automatically add its "recommended number of additional Layers" (as displayed in the Layers object editor) upon topology generation or 3D mesh generation, switch to the Automatic - Adaptive option.

 
10.6.5.1.2. Count

(applies when Insertion Mode is set to Manual - Uniform)

The number of intermediate layers to be generated and placed uniformly in the spanwise direction between the Hub and Shroud layers is specified in the Count box.

 
10.6.5.1.3. New Layer

(applies when Insertion Mode is not set to Manual - Uniform)

Clicking New Layer   (or right-clicking a layer and selecting New Layer) creates a new layer at the most suitable span location as determined by TurboGrid.

 
10.6.5.1.4. Delete Selected Layers

(applies when Insertion Mode is not set to Manual - Uniform)

Clicking Delete Selected Layer(s)   removes the selected layer(s). Hold Shift or Ctrl to select multiple layers to delete. You cannot delete the hub or the shroud layers.

 
10.6.5.1.5. Inserting Layers Automatically

(applies when Insertion Mode is not set to Manual - Uniform)

Selecting Insert > Layer Automatically from the shortcut menu for any layer object will cause Ansys TurboGrid to insert one layer automatically using built-in heuristics to determine an appropriate location. The position of the inserted layer does not depend on which layer object you right-click to access the shortcut menu.

Clicking Auto Add Layers   in the editor for the Layers object, or selecting Insert > Layers Automatically from the shortcut menu for a layer object, causes Ansys TurboGrid to insert layers automatically, using built-in heuristics to determine an appropriate number of layers to insert, and the location of each layer. The number of layers that Ansys TurboGrid proposes to add is shown in the editor for the Layers object.

To have layers inserted automatically upon topology generation or 3D mesh generation, set Insertion Mode to Automatic - Adaptive.

 
10.6.5.1.6. Inserting Layer After Selected Layer

(applies when Insertion Mode is not set to Manual - Uniform)

The Insert Layer After and Insert > Layer After shortcut menu items cause a new layer to be created at the span halfway between the selected layer and the next layer. For example, if the only existing layers are on the hub and the shroud, and Insert > Layer After is selected from the hub, Ansys TurboGrid inserts the new layer at a span of 0.5.

 
10.6.5.1.7. Span Location

(applies when Insertion Mode is not set to Manual - Uniform)

The span location of a layer can be modified in the Span Location box.

 
10.6.5.1.8. Spanwise Mesh Interpolation Guide Curves

Topological guide curves are constructed in the spanwise direction. Such curves pass through corresponding topology points on each layer. The curves can be constructed using line segments (piece-wise linear) or curves (Bspline curves). The Spanwise Mesh Interpolation Guide Curves > Type setting, which is available when not using ATM3D, controls the type of curve, and has the following options:

  • Automatic

    Chooses one of the other options automatically. TurboGrid chooses Bspline unless either of the following conditions are met, in which case it chooses Piece-wise linear:

    • The blade is ruled in the spanwise direction.

    • In the Inlet/Outlet object, Interface Specification Method > Points is selected and more than two inlet/outlet points are defined in the list of points.

  • Piece-wise linear

  • Bspline

    This option may produce adverse effects in cases with many layers.

Note:  If you have negative mesh element volumes near the leading or trailing edge of the blade, switching the curve type might correct the problem. If the problem is not corrected by switching the curve type then it is recommended that you add more layers and use the Piece-wise linear option.