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Comment on the comparison with experiment for the two angles of attack. Also,comment on the effect of mesh refinement. How does the pressure distribution over the airfoil change on increasing the angle of attack?
4. Multi-Element Airfoil
Consider a three element airfoil. Download the geometry in STEP format here: 30P30N Airfoil.
The airfoil consists of many points connected by many edges and this STEP file does not have a solid surface. Therefore, to generate the geometry, complete the details of the Import External Geometry as follows:
Make sure that Line Bodies is changed from No to Yes. This will ensure that the line bodies of the STEP file are imported into DesignModeler. After this is done, you should have 241 Parts, 241 Bodies in the Geometry Tree.
Now, select the entire 30P30N geometry using Box Select and dragging over the entire geometry.
Select from Concept > Surfaces from Edges and click Apply next to Edges to select the edges of the airfoil. After generating the surface, you should have 244 Parts, 244 Bodies in the Geometry Tree. You can go into the Geometry Tree and select all edges of the 30P30N airfoil and create a Part from them and suppress the line bodies in the part.
In the XY Plane, create a new sketch. This will be the start of the flow domain and is similar to the creation of the flow domain in this tutorial. Dimension the arc to have a radius of 3.5 m and the rectangle section to have a horizontal distance of 7 m behind the airfoil. After generating this surface, follow the same procedure outlined in this tutorial to subtract the multi-element airfoil surface body from the flow domain surface body. Close DesignModeler and open Meshing.
You should have only the surface body in the tree under geometry. Because of the way the geometry was created, there are many edges that create the airfoil. For convenience, a virtual body will be created on each element for the creation of the mesh.
Select Model in the outline tree and in the toolbar, click on Virtual Topology. Using Box Select, drag the cursor over the first element and select all edges. Right Click and select Insert > Virtual Cell. Repeat this for the remaining elements. You should see something similar to the following image:
For the second element, the right angle at the trailing edge should be independent edges and do not need to be included in the virtual cell selections. This will come in handy for the inflation layers in the mesh generation.
Now the edges have been merged for each airfoil element and edges can be selected independently.
The mesh generation is similar for this geometry as it is for the single element airfoil. Differences arise when generating the inflation layer due to the small gaps between elements. Make sure the advanced sizing function is on for curvature. Each edge will need to be sized and an inflation layer generated on each edge.