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Aircraft Aerodynamics Simulation using CFD — Step-by-Step Tutorial

Follow this practical workflow to analyze an aircraft in Stallion 3D: import your STL, set the flight condition, run a RANS simulation, and visualize CL, CD, CM, surface Cp, slices, and streamlines.

Source video: Aircraft Aerodynamics Simulation using CFD

Stallion 3D: From STL to Forces — Quick-Start Tutorial

This guided walkthrough summarizes the video and turns it into a step-by-step workflow for beginners. You’ll import an STL, set units, define the mesh & flight conditions, generate the grid, solve, and review pressures, streamlines, and forces.

Watch the reference video

Before you begin
  • 1 An STL model (ASCII or binary). OpenVSP exports work well.
  • 2 A rough idea of flight conditions (Mach, angle of attack, sideslip, temperature, pressure).
  • 3 Target mesh size (inner region near the aircraft and outer domain extents).
Step 1 — Import the STL
  1. 1 Go to File → Import → STL and select your model.
  2. 2 Open Import / Edit STL. Set:
    • Units (e.g., meters).
    • Scale, Rotation, Translation to position the model as intended.
  3. 3 Confirm the wireframe appears and surfaces look continuous.
Step 2 — Improve the view

Clarity helps spot setup issues early.

  • Enable Direct Lighting for better shading.
  • Set a white background and a darker model color for contrast.
  • Toggle surface normals if available to ensure they point outward.
Step 3 — Define the computational domain

You’ll work with two regions: an inner region around the aircraft and the outer boundary (farfield box).

Outer Boundary (Cube)

  • Extent Set the cube side length (8 times span) and Min_X, Y_min, Z_min limit.
  • Automatic optionThis can be done automatically by checking the box during STL import.

Inner Region (Near-Body)

  • Extent Set the boundary layer and cell type to cubes or right rectangular prisms around the aircraft
  • Settings A good resolution is (x, y, z) = (4,2,4) for wings with low to medium aspect ratios. Set near-body splits to 3 or 4.
Expansion & Spacing: Stallion 3D automatically sets uniform spacing in the inner region and mild growth (linear stretched) to reach the farfield without excessive cells.
Step 4 — Set flight & solver conditions

Flight Conditions

  • Mach e.g., 0.20
  • Angle of Attack e.g., +4°
  • Sideslip 0° (unless testing yaw)
  • Altitude Automatically computes initial conditions at specified altitude (standard atmosphere)
  • span class="label label-default">Fluid Type (other) Use this setting to scale for incompressible flows or set a custom compressible fluid

Solver Settings

  • Iterations Start moderate; increase if not converged.
Step 5 — Generate the grid & solve
  1. Click Generate Grid to build the mesh.
  2. Start the solver. Monitor outer/inner grids as they render and confirm coverage.
  3. Switch views (wireframe/solid) to verify the near-body grid resolves key geometry.
First-pass sanity checks:
  • Model centered in domain
  • No holes/self-intersections obvious
  • Residuals trending down
Step 6 — Visualize: slices, pressures, streamlines

Slices

Create X or Y cuts to inspect sections through the wing or fuselage and verify flow features and mesh quality.

Surface Pressure

Plot pressure contours on the aircraft. As the solution converges, patterns stabilize and highlight lift-producing regions.

Streamlines

Seed streamlines over the surface and in the wake to understand separation, upwash/downwash, and interference effects.

Step 7 — Forces, distributions & exports
  • Integrated Loads: Compute Lift and Drag at the current flight condition.
  • Parameter Sweeps: Evaluate trends vs. Angle of Attack and Sideslip to map performance envelopes.
  • Spanwise Lift: Inspect lift distribution to diagnose loading and twist/dihedral effects.
  • Reports: Export tables (e.g., to Excel) for documentation, sizing, and propulsion estimates (thrust/HP vs. speed & density).
Troubleshooting & Refinement

Common Issues

  • Slow/No Convergence: Lower CFL, increase iterations, expand outer domain.
  • Weird Pressures: Check normals, units, and AoA sign; verify STL integrity.
  • Clipped Geometry: Re-center/translate or enlarge domain extents.

When to Refine

  • Increase near-body resolution (inner region).
  • Smooth growth from inner to outer to avoid jumps.
  • Extend the farfield to reduce blockage and reflections.

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