Leading and trailing edge enhancement in Code Wand
Code Wand provides capabilities to help improve mesh quality around airfoil leading and trailing edges. These capabilities are defined by the LETE control parameter in the *.AGF file for the case and can be used to:
- Enhance existing leading and trailing edge definitions
- Create leading and trailing edges to airfoil geometries with open trailing edges
- Create trailing edges for radial impeller blades using a constant radius cut
In this article we'll summarize the options provided through the LETE parameter and outline a few use cases to help you take advantage of Wand's edge enhancement capabilities.
Managing Edge Definitions with Code Wand
Code Wand provides edge creation and refinement capabilities to assist you in improving mesh quality around the airfoil leading and trailing edges. This is accomplished with the LETE parameter specified in the *.AGF file for your case:
There are five possible values for LETE:
- "0" signifies a fully defined (closed) trailing edge that should be left untouched by Code Wand
- "1" instructs Code Wand to create a trailing edge based on the last pressure and suction side points defined in the airfoil section data
- "2" instructs Wand to create both leading and trailing edges based on the last pressure and suction side points closest to these edges
- "3" instructs Code Wand to refine the current trailing edge definition based on an arc-fitting algorithm against adjacent points at the trailing edge
- "4" directs Wand to refine both current leading and trailing edge definitions using this technique
- "-1" instructs Wand to create a constant radius trailing edge for radial impellers
Use Case 1: Edge Refinement for Fully Defined Airfoils
Let's say you are working on a turbine blade and your trailing edge definition looks as follows:
Using a text editor or the ADS Workbench, modify the LETE setting to "0" to indicate a closed trailing edge.
Generate the mesh by invoking Code Wand and inspect it using ParaView or your preferred visualization tool.
The mesh generated by Wand looks as follows:
Though it accurately represents the section data you've provided, the ridge near the suction side of the trailing edge gives you concern.
Rather than rework the airfoil geometry to eliminate the ridge, you can instruct Code Wand to automatically enhance the trailing edge definition for you. This is accomplished by setting LETE to "3". When LETE is set to this value, Code Wand refines the trailing edge definition by determining how and where best to apply an arc against the supplied trailing edge section data.
Change the value of LETE to "3" and invoke Code Wand to regenerate the mesh.
The regenerated mesh looks as follows:
The trailing edge now smoothly integrates with the suction surface, eliminating the unwanted ridge.
Use Case 2: Edge Creation for Axial Airfoils with Open Leading/Trailing Edges
You can also rely on Code Wand to create edges by providing airfoil section data with an open trailing (or leading) edge. This is accomplished by setting LETE to "1" or "2". By setting LETE to "1", a semi-circle with a diameter equivalent to the distance between the last pressure and suction side points on the trailing edge will be added. By setting LETE to "2", semi-circles will be generated for both the leading and trailing edges.
Let's take a look at an example of how this can be used to create a trailing edge for an airfoil. Suppose we have created section data for an airfoil with an open trailing edge:
Using the AGF file for the case or the ADS Workbench, we set LETE to "1" and regenerate the mesh.
The resulting mesh looks as follows:
Use Case 3: Edge Creation for Radial Impeller Blades with Open Trailing Edges
One particularly useful feature for radial turbine and centrifugal compressor designers is the ability to rely on Code Wand to create trailing edges for impeller blades with constant radius cuts. This is accomplished by setting LETE to "-1" and by providing airfoil section data with open trailing edges. This feature can be applied to the main blade as well as to all splitters.
Let's take a look at an example of how this can be used to create trailing edges for a radial impeller with one main blade and three splitter blades. A plot of the section data for the main blade with open trailing edges case be seen below:
Using a text editor or the ADS Workbench, set the value for LETE to "-1" to instruct Wand to create trailing edges for the impeller blades at a constant radius:
Invoke Code Wand to generate the mesh. As can be seen from the diagrams below, Wand creates trailing edges for each impeller blade at constant radius: