How to Analyze an Aircraft in Stallion 3D

Instructions

1. Import the aircraft geometry

1. Open Design.
2. Click Input / Import / Edit STL File.
3. Select the aircraft STL file.
4. Use either ASCII or binary STL format.
5. If needed, use an STL exported from OpenVSP.

2. Set the aircraft dimensions

1. Check the size of the imported aircraft.
2. Scale the STL to the correct physical dimensions.
3. Click OK after the dimensions are correct.
4. Remember that STL files do not include dimensions automatically.

3. Check the wireframe

1. Return to the Design menu.
2. Display the wireframe view.
3. Confirm that the aircraft appears correctly before solving.

4. Open the CFD solver setup

1. Open the CFD Solver menu.
2. Use Stallion 3D automatic grid generation for the surface and volume mesh.
3. For a first run, choose a small grid of about 500,000 cells.
4. If needed, use larger grids up to about 2 million cells or more.

5. Define the grid shape

1. Select a Cartesian grid.
2. Set the outer boundary cell layout to 4 cells in X, 2 cells in Y, and 4 cells in Z.
3. Use meters for the dimensions.
4. For the example aircraft, set the longest side length to 72 m.

6. Keep the default flow solver

1. Use the default Navier-Stokes solver.
2. The default method is a second-order Navier-Stokes solver.
3. The turbulence model uses a wall function based on k-epsilon.
4. No extra change is required for this basic setup.

7. Generate the grid and solve the flow

1. Return to the CFD Solver menu.
2. Click the option to Generate the Grid.
3. Start the flow solution.
4. For the example shown in the video, good convergence is obtained after about 3,000 iterations.
5. On an ordinary laptop, the run time is about 2 to 3 hours.

8. View the 3D solution

1. Open the Visualization menu.
2. Select View 3D.
3. Inspect the computational mesh.
4. Inspect the aircraft surface pressure distribution.

9. Read the aerodynamic results

1. Open the aerodynamic data output.
2. Read the lift coefficient.
3. Read the drag coefficient.
4. Read the lift-to-drag ratio.
5. Read additional values such as pitching moment and roll coefficient.

10. Read the aerodynamic forces

1. Check the force results based on speed, altitude, and aircraft size.
2. For the video example, the computed lift force is about 1,691 lb.

11. Repeat with improved settings if needed

1. If the first run looks reasonable, repeat the case with a finer grid.
2. Change the flight condition if you want results at another speed or angle of attack.
3. Use the same workflow for other imported aircraft geometries.

Short Summary

The basic workflow is: import the STL, scale the aircraft, inspect the wireframe, set the CFD grid, generate the mesh, solve the Navier-Stokes equations, and then review pressures, coefficients, moments, and forces.