CFD Analysis: RQ-4 Global Hawk UAV

Overview

This study analyzes airflow around the Northrop Grumman RQ-4 Global Hawk, a high-altitude UAV, using ANSYS Fluent CFD software. It examines aerodynamics at Mach 0.39 (cruise speed ~357 mph) and 5° angle of attack to understand lift, drag, and flow patterns.​

Geometry and Mesh

• Model: Created in SpaceClaim, imported to Fluent Meshing.

• Mesh Quality: 3.76 million elements; 10 boundary layer rows for near-wall accuracy; min orthogonality 0.18.

• Domain: Symmetric setup with far-field boundaries.

Simulation Setup

• Solver: Pressure-based, ideal gas air, steady-state.

• Boundaries:

  Boundary	Condition
  UAV Surface	No-slip wall
  Inlet/Far-field	Pressure far-field (M=0.39, α=5°)

   

   

• Methods: SIMPLE coupling, standard initialization.

• Extras: Includes FSI analysis and RBF-morph wing optimization for lift-to-drag ratio.

Key Results

• Velocity: Boundary layers form; wake develops behind UAV with vortices (Fig 3).​

• Pressure: Higher on lower wing (compressed air); lower on upper wing (faster flow → lift via Bernoulli) (Fig 4).​

• -14m Plane Analysis:

  • Pressure coefficient: Peak at leading edge stagnation (Fig 5).

  • Pressure contour: High near leading edge (Fig 6).

  • Velocity contour: Zero at stagnation, accelerates along surface (Fig 7).

• Forces: Lift = 199,110 N; Drag = 47,516 N (L/D ≈ 4.2 at these conditions).

Conclusion

The analysis confirms expected aerodynamics: pressure difference generates lift; wake causes drag. High-quality mesh ensures reliable results for design optimization. Matches Global Hawk specs (wingspan 131 ft, cruise 357 mph, ceiling 60,000 ft).