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Helicopter Technology
Performance, efficiency and safety for rotorcraft
n
Helicopter rotor blades operate in a wide range of flow conditions, but with a fixed geometry
which is optimized only for a small sub-set of the complete flight regime. An obvious way to
increase the efficiency of conventional rotors would be an adaptive blade geometry which allows
selection of the optimal shape in terms of power or thrust. The European Commission has awarded
a research contract to a team of universities and research institutions including the Institute for
Helicopter Technology to investigate solutions for morphing rotor blades during the coming
42 months. A group of four researchers will develop models for such morphing structures and
validate their simulations with experimental results.
Rotorcraft Downwash and Dynamic Interface Modeling
for Real-Time Simulations
Rotorcraft downwash – as the flow field below the rotor
disc is usually called – and more specifically its effect on
the aircraft is perceived by pilots as so-called ‘ground
effect’. In simulation models, this effect is mostly rep-
resented by a dependency of the lift on the distance
between rotor and ground. Pilots operating on ship decks,
oil rig platforms or wind energy platforms experience,
however, a time-varying version of this ground effect
which requires higher piloting skills and more training.
Commercial pilot training simulators do not represent
this dynamic behavior at a satisfactory level since they
lack physics-based downwash models. The Institute
for Helicopter Technology has realized the coupling of
a novel Lattice-Boltzmann based fluid simulation model
with external air wake – from ship decks, platforms, etc.
– and rotor aerodynamics (inflow) modeling, including the
feedback on the flight dynamics and handling qualities
for piloted simulation of rotorcraft. A research grant from
the U.S. Office of Naval Research enables a cooperation
with the U.S. Naval Academy and the George Washington
University who contribute valuable experimental data to
support and validate our simulation results. Funded by
the German Ministry of Economic Affairs and Energy, this
modelling approach is additionally pursued with a target
application on platforms in offshore windfarms. Partners
are DLR and the Universities of Stuttgart and Tübingen.
Modelling and Testing of Counter-Rotating Rotors
Co-axial (also known as counter rotating rotors)
are still a rare species of rotorcraft. But there are
some undisputable advantages like symmetry
and its associated ease of flying or high speed
potential which make them increasingly attractive.
Modelling such rotors is particularly challenging
due to the obvious interaction between the
adjacent rotor disks. Therefore, model validation
based on experimental data is a pre-requisite.
For the Institute of Helicopter Technology, two
different data sources are available:
An ultra-light (max. 450kg) 2-seater rotorcraft
is modelled, flight tested and evaluated under
a grant from the German Federal Ministry for
Economic Affairs and Energy with the aim to
better understand the limits of the flight envelope
of this type of rotorcraft.
But co-axial rotor configurations are also viable
candidates when aiming at the high-speed flight
regime. Therefore, the existing cooperation with
the University of Texas has been continued under
the umbrella of VLRCOE.
Blade clearance vs. flight speed