Example: Aircraft Wing Analysis

Example: Aircraft Wing Analysis#

This example demonstrates an external aerodynamics analysis of an aircraft wing section — computing lift and drag, visualizing the pressure coefficient distribution, and examining flow patterns.

Objective#

  • Generate a mesh around a wing geometry

  • Run a RANS simulation at a given angle of attack

  • Compute lift and drag coefficients (Cl, Cd)

  • Visualize pressure coefficient (Cp) distribution on the wing surface

  • Examine tip vortex structure (for 3D wings)

Step 1: Create a Meshing Project#

  1. Dashboard → New Project → Meshing

  2. Name: “Wing Analysis”

  3. Upload your wing geometry (STEP recommended)

Step 2: Domain Configuration#

In the Setup tab:

  1. Select External Flow domain type

  2. Choose Box domain shape (or C-Domain for 2D-like airfoil sections)

  3. Configure domain dimensions:

Parameter

Value

Reasoning

Upstream

5× chord length

Adequate approach distance

Downstream

10× chord length

Capture the full wake

Span direction

3× semi-span (or periodic for infinite wing)

Avoid tip effects on boundaries

Above/Below

5× chord length

Prevent blockage

For a half-wing with symmetry:

  • Enable symmetry plane at the wing root

  • This halves the domain and cell count

Step 3: Refinement Zones#

Leading Edge Zone#

  • Shape: Box

  • Position: Enclosing the leading edge, extending 0.1× chord upstream

  • Cell size: 4× finer than base mesh

  • Purpose: Capture the stagnation point and leading edge suction peak

Trailing Edge / Wake Zone#

  • Shape: Box

  • Position: Behind the trailing edge, extending 2× chord downstream

  • Cell size: 3× finer than base mesh

  • Purpose: Resolve the wake and any trailing edge separation

Tip Region (3D wings)#

  • Shape: Cylinder

  • Position: Around the wing tip

  • Cell size: 3× finer than base mesh

  • Purpose: Capture the tip vortex structure

Step 4: Surface Naming#

Surface

Name

Wing upper surface

wing_upper or wing

Wing lower surface

wing_lower or wing

Far-field boundaries

inlet, outlet, farfield

Symmetry plane

symmetry

Step 5: Mesh Settings#

Parameter

Value (for ~1 m chord)

Target cell size

0.05 m

Min cell size

0.002 m

Refinement levels

10

Boundary layers

Enabled

Number of layers

12

First layer height

0.00005 m (y+ ≈ 1 for resolved BL)

Growth rate

1.15

Tip

For wing analysis, a resolved boundary layer (y+ ≈ 1) provides more accurate lift and drag predictions than wall functions (y+ ≈ 30). Use more boundary layers (12–15) with a smaller first layer height.

Step 6: Generate Mesh and Create CFD Project#

  1. Generate the mesh (expect 5–20 million cells for a medium-resolution wing)

  2. Create a new CFD project using this mesh

Step 7: Simulation Setup#

Setting

Value

Turbulence model

k-ω SST

Inlet velocity

Set to achieve desired Reynolds number. For Re = 6M at 1 m chord: ~88 m/s

Angle of attack

Set via velocity direction components (e.g., Ux = V cos(α), Uz = V sin(α))

Outlet

Pressure outlet, 0 Pa

Wing surface

No-slip wall

Far-field

Slip wall

Symmetry

Symmetry condition

Turbulence intensity

0.1% (clean wind tunnel)

Max iterations

1500

Setting Angle of Attack#

To simulate at α = 5° with freestream velocity V = 88 m/s:

  • Ux = 88 × cos(5°) = 87.66 m/s

  • Uz = 88 × sin(5°) = 7.67 m/s

Set these as the inlet velocity components.

Step 8: Results Analysis#

Lift and Drag Coefficients#

  1. Forces tool → Select wing surface

  2. Reference values:

    • Reference velocity: Freestream speed

    • Reference area: Wing planform area (chord × span)

  3. Read Cl and Cd

Validation

NACA 0012 at Re=6M, α=5°

Expected Cl

~0.55

Expected Cd

~0.008

Pressure Coefficient Distribution#

  1. Color the wing surface by Pressure

  2. Look for:

    • Suction peak near the leading edge on the upper surface (low Cp)

    • Pressure recovery toward the trailing edge

    • Stagnation point on the lower surface near the leading edge (Cp ≈ 1)

Flow Visualization#

  • Slice plane at mid-span, colored by velocity → Shows the flow acceleration over the upper surface and the wake

  • Streamlines seeded upstream → Shows how flow divides at the stagnation point and flows over/under the wing

  • Isosurface of low pressure near the wing tip → Reveals the tip vortex core

Span-wise Analysis#

For a 3D wing, use line probes at different span stations to compare:

  • Cp distribution at root, mid-span, and tip

  • How the lift distribution varies along the span

  • Where stall initiates (typically from the tip inward)

Angle of Attack Sweep#

To generate a lift curve (Cl vs. α):

  1. Run simulations at several angles (e.g., 0°, 2°, 5°, 8°, 10°, 12°)

  2. Record Cl and Cd from each run

  3. Plot Cl vs. α — the slope should be approximately 2π per radian in the linear region

  4. Identify the stall angle where Cl drops sharply

Stall Prediction

RANS models (especially k-ω SST) predict stall onset reasonably well but tend to over-predict the maximum Cl. For accurate post-stall behavior, consider LES or DES (available on Pro tier and above).

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