European Strategic Wind tunnels
Improved Research Potential
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European Transonic Wind Tunnel
Description of the infrastructure:
The ETW uniquely achieves real flight conditions for
transport aircraft at model scale. Thus, ETW data have been
demonstrated to match flight test data better than 99%. This
unique accuracy is gained by cryogenic pressurised operation
of the wind tunnel from low speed to a maximum speed of Mach
1.3 at real-flight Reynolds numbers. Using ETW, researchers
are able to check scientific concepts for applicability at
real-flight conditions effectively and efficiently at low
risk. So, ETW contributes to increase aeronautic innovation
speed, and enables research to provide breakthrough
technologies for ecological and economical optimisation of
future air transport.
The ETW is in operation since 1994. The test section
dimensions are 2.0m x 2.4m (height x width). The test medium
nitrogen gas can be pressurised up to 4.5 bar and cooled
down to 110K. The flow is propelled by a multistage
compressor driven by an external electric synchronous motor
with a maximum power output of 50 MW. Currently, ETW has two
exchangeable model carts for full model support, which
enable testing at Mach 0.8 up to 50 and 85 million in
Reynolds number, matching flight conditions of aircraft as
large as the Airbus A340 and A380, respectively. One of the
model carts is adapted to allow also half-model testing. By
variation of pressure and temperature flow parameters like
Mach Nr, Reynolds Nr and dynamic pressure can be varied
independently. This enables a distinct separation of
compressibility effects, friction effects and model
deformation effects. All model carts employ a common test
section box consisting of a floor and side-walls.
Flow separation and its interaction with e.g. the model
deformation or shock waves in the flow field in general is
highly Reynolds number dependent. Unsteady interaction may
occur which then initiates model vibrations. These physical
phenomena often determine the flight envelope boundary of
aircraft, and thus its understanding and control is subject
of aeronautical research. Compared with CFD and conventional
wind tunnels, the ETW wind tunnel circuit itself uniquely
facilitates to take into account these phenomena at flight
relevant conditions. The proposed service improvements will
enable researchers to make best use of these capabilities:
The considered upgrade in test capability will significantly
enhance ETW’s capability to investigate unsteady
fluid-structure interactions for take-off and landing as
well as cruise speed conditions at a high level of quality
and productivity. Thus, the considered upgrade will enable
the European research and development community to gather
more detailed and accurate information about complex flow
fields and fluid-structure interactions as well as the
resulting effects on aircraft performance and behaviour at
design and off-design flight conditions.
The considered upgrade by installation of a remotely
controlled wall-slot setting will lead to a substantial gain
in tunnel accessibility, operational flexibility and
productivity. This improvement is generally of major benefit
to all customers and will specifically allow to integrate
shorter test campaigns in existing operating schedules
without requiring tunnel access and, hence, representing
cost and time savings.