Simulation
Helicopter Rotor Aerodynamics
Efficient modelling of unsteady aerodynamic loads on a helicopter rotor for multibody simulation, combining blade-element theory with vortex wake methods and validated against wind-tunnel and flight-test data across multiple flight conditions.
The Problem
A helicopter rotor operates in one of the most aerodynamically demanding environments in engineering. The flow seen by each blade changes continuously with azimuth angle, forward speed, blade motion, induced velocity, wake geometry, dynamic stall, blade-vortex interactions, fuselage interference and ground effect. Modelling this environment with full CFD fidelity would be too expensive to couple to the structural dynamics of a general-purpose multibody rotor model.
The goal of this master's thesis was to find a useful engineering compromise: accurate enough to capture the dominant unsteady rotor phenomena, computationally efficient enough to be embedded in a multibody simulation loop.
Aerodynamic Model Stack
The model is built in layers of increasing complexity. Blade-element theory forms the foundation, computing local sectional airloads from the velocity seen by each blade section. Unsteady aerodynamic corrections handle both attached flow and dynamic stall onset. Inflow models range from simple momentum-theory approaches to dynamic inflow models that capture the time history of induced velocity changes.
At the most detailed level, prescribed and free vortex wake models capture the three-dimensional induced velocity field produced by the trailing and shed vorticity from each blade. A source-panel model handles rotor-fuselage aerodynamic interaction, and an image-method approach models the ground effect during take-off and landing.
The different models were compared in terms of accuracy and computational cost and validated against wind-tunnel measurements and flight-test data across several flight conditions.
Key Finding
Vortex-based methods performed well across all studied flight conditions, particularly where blade-vortex interactions (BVI) were significant — a phenomenon responsible for the characteristic helicopter sound. The computational cost was higher than simpler inflow models but remained compatible with coupling to multibody simulation.
Connection to Later Work
The core trade-off encountered here — model fidelity versus computational speed, and the question of how much physics is enough — became a recurring theme in subsequent work on gear contact simulation, bearing dynamics, and model order reduction. The specific domain changed; the engineering challenge remained the same.