Creating a Spherical Far-Field Boundary

In this tutorial, you create a sphere where the outer surface represents the far-field conditions of the flow.

In typical numerical studies of aerodynamic performance, the distance from the wing to the far-field boundaries is taken as 10 times the chord length. In this tutorial, in order to reduce the computational time, the far-field distance is set to 5 times the chord length.

To create a spherical fluid domain:

  1. In the object tree, right-click the Geometry > 3D-CAD Models > Onera M6 Wing node and select Edit.

    The 3D-CAD environment launches. Within 3D-CAD, an object tree that is specific to the 3D-CAD model is displayed.

  2. Create a plane by transformation for the domain:
    1. Right-click the Features > ZX node and select Reference Geometry > Plane by Transformation.
    2. In the Plane By Transformation panel, set the Translation Vector to [0.0, 0.0, 0.2] and click OK.
    A sketch plane feature, Plane 1 is added to the Features node.
  3. Create a sketch for the domain:
    1. In the 3D-CAD feature tree, right-click the Plane 1 node and select Create Sketch.
    2. In the Sketch panel, click (View Normal to Sketch Plane).
    3. Within Display Options, click Set Sketch Grid Spacing. In the dialog, set Grid Spacing to 10.0 m, Number of fine grid divisions to 1.0, and click OK.
      In the 3D-CAD View scene, zoom out until you can see 5 grid boxes on either side of the origin.
    4. Use the (Create Center-Point Circular Arc) tool to draw an arc with a radius of 50 m. Three mouse clicks are required:
      1. Click position [0.0 m, 0.0 m] to define the center point.
      2. Click position [50.0 m, 0.0 m] to define the start point.
      3. Click position [-50.0 m, 0.0 m] to define the end point.
    5. Click (Create Line) and draw a horizontal line of length 100 m starting at -50 m and ending at 50 m and passing through the origin. To end the line, press <Esc>.
    6. Right-click the line and select Set As Construction.


    7. In the Sketch panel, click OK.
  4. Use the revolve tool to create the sphere:
    1. In the 3D-CAD feature tree, right-click Sketch 1 and select Revolve.
    2. In the Revolve panel, set Angle to 180.0 deg and click OK.
    3. In the 3D-CAD View scene, rename the new surface to Farfield. (To rename a surface, right-click the surface and choose Rename).
  5. In the Vis toolbar, click (Save-Restore-Select Views) and select Standard Views > (-Y) left.
  6. Use the fill hole tool to cap the sphere and convert it to a solid body:
    1. In the 3D-CAD View scene, double-click the free edge (displayed in green) to select all connected free edges.
    2. Right-click the selection and choose Fill Surface.
    3. In the Fill Surface panel, click OK.
    4. In the 3D-CAD View scene, rename the new surface to Symmetry.
  7. To create the fluid volume:
    1. Under Body Groups, right-click the Body 2 node and select Boolean > Subtract .
    2. In the Subtract Bodies panel, to the right of the Tool Bodies selection box, click (Open Selector).
    3. Within the Select Tool Bodies panel, select Body 1. Click (Close Selector).
    4. Click OK.
  8. Under the Body Groups node, rename the Body 2 node to Fluid.
  9. At the bottom of the object tree, click Close 3D-CAD.
  10. Save the simulation.