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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 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. ...[more]

Transonic buffet, an unsteady shockwave oscillation phenomenon that occurs at transonic flow speed, determines the upper limits of an aircraft’s flight envelope and causes undesirable vibration on an aircraft. It also has a considerable effect on a rocket’s payload vibration environment inside the fairing during launch. Optimizing the configuration of aircraft and launch vehicles using aerodynamic devices to improve aerodynamic characteristics and expand the corresponding flight range would make it possible to increase overall safety.

JAXA has constructed unsteady PSP and time-resolved PIV - two approaches to optical measurement technology to investigate shockwave oscillation and other unsteady flow fields - to develop technologies for identifying where buffet occurs in three-dimensional flow fields and evaluating the detailed structure of flow fields. The Figures below show a rocket fairing model in the JAXA 2m x 2m Transonic Wind Tunnel and the corresponding unsteady PSP-based pressure fluctuation test measurements and time-resolved PIV-based instantaneous velocity field measurements.

Using unsteady PSP, time-resolved PIV, and other technologies capable of producing detailed flow field measurements, JAXA will also conduct experiments to develop optimization methods for determining ideal device configurations and arrangements in designing devices to overcome transonic buffet issues.

Rocket fairing model (the white area is the PSP measurement range)

Unsteady PSP measurement results (Mach number: 0.8; angle of attack: 4°; 1/500 slow motion)> Video: The significant pressure on the model causes fluctuating oscillation

Time-resolved PIV measurement results (Mach number: 0.8; angle of attack: 0°; 1/2000 slow motion) Video: The high velocity acting on the model causes fluctuation (particularly in the blue denuded area)

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