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Fixed-Wing Drone Aerodynamics Analysis

Learn how to analyze the aerodynamic performance of a fixed wing drone with Navier AI’s platform.

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Quick Start Guide

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Simulation Objectives

  • Calculate total drag force on the drone body
  • Analyze rotor downwash effects
  • Evaluate aerodynamic efficiency
  • Optimize drone design for performance

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Expected Results

  • Drag Coefficient: Typical values range from 0.3-0.8 for drone bodies
  • Rotor Efficiency: Thrust-to-power ratios
  • Flow Visualization: Rotor wake and body interaction patterns

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Geometry Preparation

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CAD Requirements

Your drone geometry should include:
  • Main Body: Fuselage/frame structure
  • Rotors: Either as solid disks or detailed propeller geometry
  • Landing Gear: If significant to overall aerodynamics

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File Export Tips

Export Settings (STL):
- Resolution: Fine (small triangles for curved surfaces)
- Units: Meters (platform default)
- Coordinate System: Z-up, X-forward
- File Size: Keep under 50MB for best performance
Rotor Modeling: For efficiency, model rotors as solid disks rather than detailed blades. Use boundary conditions to simulate rotor effects.

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Mesh Configuration

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1. Geometry Upload

  1. Create new project: “Drone Aerodynamics Analysis”
  2. Upload your drone STL file in the Geometry section
  3. Verify orientation in 3D viewer (X = forward, Z = up)

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2. Domain Setup

Recommended Settings:
  • Preset: Medium Domain
  • Flow Direction: X-axis (forward flight)
  • Domain Factors:
    • Upstream: 10× (allows flow development)
    • Downstream: 20× (captures wake)
    • Lateral: 8× (accounts for rotor effects)
ParameterSmall Drone (< 0.3m)Medium Drone (0.3-1m)Large Drone (> 1m)
Base Cell Size0.02m0.05m0.1m
Upstream8× length8× length8× length
Downstream15× length15× length15× length
Lateral6× width6× width6× width

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Base Mesh

  • Cell Size: Start with 0.1m base mesh
  • Geometry Refinement: 3 levels around drone body
Zone TypePurposeSizeLevel
Surface (Geometry)Boundary layers & featuresAutoGlobal: 2, Max: 3
Wake (Box)Downstream flow4×1.5×1.5 drone size2
Near-Body (Box)Flow around drone2×2×2 drone size1
Create cylindrical zones around each rotor:
  • Type: Cylinder
  • Radius: 1.2× rotor radius
  • Height: 3× rotor diameter (above and below)
  • Refinement Level: 4-5
Capture downstream wake effects:
  • Type: Box
  • Position: Behind drone
  • Dimensions: 2× body width, 5× body length
  • Refinement Level: 3-4
High resolution near drone surfaces:
  • Type: Geometry-based
  • Distance Levels:
    • Level 5: 0-0.1m from surface
    • Level 4: 0.1-0.3m from surface
    • Level 3: 0.3-0.8m from surface

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4. Solver Configuration

  • Flow Type: Incompressible (for typical drone speeds < 50 m/s)
  • Simulation Mode: Steady State
  • Turbulence Model: k-ω SST (good for external aerodynamics)
  • Convergence: 1000-2000 iterations

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5. Boundary Conditions

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Domain Boundaries

Inlet (Upstream):
- Velocity: 10-30 m/s (typical flight speeds)
- Turbulence Intensity: 1-5%
- Direction: X-axis

Outlet (Downstream):
- Pressure: 0 Pa (gauge)
- Zero gradient for other variables

Side Walls:
- Symmetry or slip walls

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Drone Surfaces

Body/Frame:
- No-slip wall condition
- Wall functions for turbulence

Rotor Disks (if modeled):
- Fixed velocity (thrust direction)
- Or momentum source term
Rotor Modeling: For spinning rotors, consider using momentum disk theory or rotating reference frames for more accurate results.

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Running the Simulation

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Pre-flight Checks

  • Geometry properly positioned and oriented
  • Domain size adequate (no boundary effects)
  • Mesh quality acceptable (orthogonality > 0.1)
  • Boundary conditions physically realistic

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Monitoring Convergence

Watch for:
  • Residuals: Decreasing to < 1e-4
  • Force Coefficients: Stable values after ~500 iterations
  • Mass Flow: Conservation at inlet/outlet

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Typical Runtime

  • 2-4 million cells: 30-60 minutes
  • 8-15 million cells: 2-4 hours
  • Convergence: Usually within 1000 iterations

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Results Analysis

Switch to “Post-Processing” tab to analyze results.

Drag Force

Total drag force on drone body in NewtonsTarget Range: 0.5-2.0 N for small drones

Drag Coefficient

Non-dimensional drag coefficientFormula: CD = 2F/(ρV²A) Typical Range: 0.3-0.8

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Design Insights

IssueSymptomsSolutions
High DragCD > 0.8Streamline body, round edges
Flow SeparationLow pressure regionsSmooth transitions, reduce angles
Poor EfficiencyHigh power requirementMinimize frontal area

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Validation Checklist

Reduce Drag:
  • Streamline body shape (rounded edges)
  • Minimize frontal area
  • Smooth surface transitions
  • Optimize rotor positioning
Improve Efficiency:
  • Reduce rotor-body interference
  • Optimize prop spacing
  • Consider ducted rotors
  • Minimize landing gear drag

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Validation and Best Practices

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Mesh Independence Study

Run simulations with progressively finer meshes:
  1. Coarse: ~1M cells
  2. Medium: ~3M cells
  3. Fine: ~8M cells
Results should converge within 5% between medium and fine meshes.

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Physical Validation

  • Compare with experimental data if available
  • Check conservation laws (mass, momentum)
  • Verify Reynolds number appropriateness
  • Validate boundary layer resolution (y+ < 300)

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Next Steps

Rotor Analysis

Learn advanced rotor modeling techniques with momentum theory

Optimization Study

Set up parametric studies for design optimization

Unsteady Analysis

Analyze time-dependent effects and rotor interactions

Heat Transfer

Add thermal analysis for motor cooling studies
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