European Strategic Wind tunnels
Improved Research Potential
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ONERA S1
Description of the infrastructure:
The ONERA S1MA wind tunnel facility is the largest transonic wind tunnel in the world. It is a closed circuit atmospheric wind tunnel with a maximum speed near Mach 1. The ONERA S1MA provides unique capabilities for testing large models at cruising speed and above. The tunnel was erected after the Second World War and has three exchangeable test sections with a diameter of 8m, which can be transformed into 5 different test section configurations. The air in the tunnel is propelled by two large fans each connected by means of a shaft to a Pelton turbine outside the tunnel circuit. The turbines with a maximum power output of 88 MW are driven by a controlled flow of water extracted from a reservoir above the tunnel. The major benefits of S1MA are :
- It's size: The S1MA facility (the biggest in the world for its velocity range) can accommodate in its test section very large models. The benefit of having large models is essential for testing new concepts and having enough room within the models for housing various devices such as boundary layer control devices, remotely actuated mechanisms, drag reduction devices; aircraft control mechanisms both for handling qualities and efficiency improvement, laminar flow concepts etc.
- It's performances: The S1MA facility can operate up to sonic Mach number at atmospheric pressure. Civil transport aircraft developed over the last decades have been designed with a consistently increasing maximum flying speed.
The benefits retrieve from experimental works performed at
S1MA are essential to the researchers and aircraft
manufacturers, to the future of the European aeronautic and
all together to the harmonious development of Europe and the
welfare of its citizens. In that respect it represents a
strategic facility which must be closely looked at in terms
of capabilities to fulfil the increasing complex
requirements for progress of its users.
The existing temperature control process of the ONERA S1MA
works according to the following principle: air from outside
enters the circuit through ventilation openings upstream of
the test section and mixes with the main flow. In practise,
this leads to restrictions in operational availability of
the tunnel as the outside air may be humid and has
sometimes, in peculiar weather conditions, a rather high
dew-point, which at near sonic conditions may lead to the
occurrence of so-called condensation shockwaves in the flow
over models. As a consequence, in adverse weather conditions
at high speed, the tunnel must go through a warm-up phase
resulting in a waste of time and energy. A second phenomena
is the difficulty to maintain a perfect constant Mach number
in the test section during a test run resulting in long and
expensive procedures to obtain high quality test data. The
Mach number in the test section varies as a result of both
the natural flow instabilities of the tunnel and the
continuous variation of model attitude. The ultimate goal of
the proposed upgrade is to make this top quality testing
available to the users on more permanent basis, and at
reduced costs.
The proposed upgrade of S1MA aims at improving the wind
tunnel quality and productivity by implementation of a
closed loop Mach number control system. The work will be to
determine the best control strategy via a modelling of the
flow behaviour and then to design and implement a control
mechanism.
Userguide (under construction)