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Innovation in wind tunnel testing

ONERA Testing Services Expand Customer Expectations of Wind Tunnel Tests

ONERA (The French Aerospace Lab) has operated a suite of world-class wind tunnels for over 55 years, within its GMT division.  This division is managed on the basis of a corporate approach. It's the division's responsibility to provide customers with testing services (both model and test) which will meet, anticipate and in some cases expand their present and future expectancies. Our service is much more than just the wind tunnel capabilities.

Our first priority is always to answer, in the most appropriate cost-effective manner the primary objectives of a client.  But we are forever mindful of the global competition we face, and therefore we are always looking for ways to offer more value per test to our customers.  It has become the "norm" to see wind tunnels improve productivity, and our focus is on expanding customer expectations.

A new flying vehicle today is the result of an optimization between various disciplines and requirements. We see the wind tunnel as a powerful tool for reducing risk in the design phase, and to promote innovation.  We are committed to assisting our customers in developing technology, and minimizing the budgets necessary to do so. Our testing services help a project  progress along a "clarity line", which is crucial when trying to assess the potential of a new technology, to provide a commercial advantage before committing to its development.

Wind tunnels testing has already changed significantly over the last 50 years. We are no longer just providing forces, moments, and pressures. Test campaign optimization is the "norm" today, meaning our customers are focusing their testing on the difficult areas of the flight envelope, which CFD cannot model adequately. The experimental methods already developed, and GMT's ongoing quest for improved testing techniques and measurements, are key issues to expanding customer expectations for this focused testing. Sustained effort has been put into specific areas, with a clear desire for progress beyond current limitations in both the model design and test. In particular, we are referring to Model Deformation Measurements (MDM); Particle Imaging Velocimetry (PIV) flow measurements; Pressure Sensitve Paint (PSP) global measurement techniques (both steady and dynamic), improved data corrections of wind tunnel sting and wall effects, aero-acoustics and model automation.

One area of customer expectations, we hope to expand, is the full commercialization of global measurement techniques, such as PIV and low-speed PSP.  These techniques will provide extensive pressure distributions, local loading, flow mapping around the model, propulsion integration effects, etc.  In low-speed use of PSP we have overcome issues of pressurized environment, high temperature sensitivity, low pressures to measure, and long optical paths.  After several years of effort, the measurement technique is now being offered to customers, as shown below.

The marriage between wind tunnels and CFD is now well established, and the limitations to CFD are better realised.  The wind tunnel will remain a significant part of the investment in project risk reduction.  Continually  expanding the expectations of our customers is, we think, the best way to promote utilization of wind tunnels in the future, and remain competitive in a world market as a result.