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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.


Model design handbook


Enhancement of the Stereo Pattern Tracking Technique for Model Deformation Assessment at ETW