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Japan Aerospace Exploration Agency

Technology for evaluating and improving transonic unsteady flow fields

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September 25, 2014

PIV measurement data aids device arrangement design Wind tunnel tests to develop optimization technology

The arrangement of devices such as a vortex generator*1 on the wing of an aircraft usually requires repeated wind tunnel tests in the design stage to determine the optimal arrangement to yield the best aerodynamic characteristics.
By making use of high-density, precise measurement data obtained by particle image velocimetry (PIV)*2, JAXA has been able to conduct research and development on methods to determine arrangements that enable such devices to have good aerodynamic characteristics and to do so in a shorter period of time and with better reliability than ever before.
In PIV measurement tests conducted using the JAXA 2m × 2m transonic wind tunnel in June 2014, we observed clear differences in the airflows generated with and without vortex generators, as well as the airflow variations due to the arrangement of the generators. Using this data, we plan to proceed with R&D to derive a highly effective arrangement of these devices.

*1 A vortex generator is a projecting vane attached to the wing of an aircraft to cause a vortex in the airstream and to control the flow of the air foil surface.
*2 PIV is a technique for measuring the velocity of fluid flow by seeding tracer particles into the flow and analyzing images of their motion as recorded with illumination from a light source such as a laser. (See page 15)

Airflow velocity measurement results (Color coded in sequence from the fastest speed down to the slowest in red, yellow, and yellow-green.)
When there are no vortex generators, the slow airflow area that can be seen colored in yellow and yellow-green (bottom image) becomes smaller when a vortex generator is used (top image).

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