Application of pressure sensitive paint technique in the S1MA ONERA wind tunnel

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The paper discusses in a first part the ONERA choices in regard to paint, hardware and software. Advantages of a two component paint are demonstrated, and major steps of data reduction are described. In a second part, the paper reports the implementation of PSP in the large (8m in diameter) SI MA subsonic wind tunnel. The tests performed in 99 on a transport half model were the first application of PSP in SI. The test conditions are more severe in this large tunnel than in S2MA in several respects: the model illumination shall be powerful enough to compensate for the larger distance between the model surface and the illumination source, the flow temperature is not controlled and may reach 60°C ; the optical equipment (cameras, optical fiber, light source) shall be protected from the tunnel vibrations ; and the natural daylight intensity (i.e.the darkness reference) does vary significantly throughout the day. Corrections of test results for temperature level effects and for daylight variations were developed and applied. The tests results were judged very satisfactory in terms of repeatability and comparison with conventional pressure measurements. Recently, a new test campaign was successfully performed on a full model of a transport aircraft mounted on the tripod support of the wind tunnel. The upper surface of the right wing was completely covered by PSP as well as the lower surface of the wingtip flaps. Results obtained during this test are shown and the capability to use PSP for hinge moment measurement is demonstrated. Copyright © 2001 by the American Institute of Aeronautics and Astronautics Inc. All rights reserved INTRODUCTION Pressure sensitive paints have been recognized about 10 years ago as a potentially attractive tool for pressure measurements on model surfaces in wind tunnel testing. The advantages of PSP technology are obvious: not only does it offer a continuous coverage of the surface under consideration as long as it is optically accessible, but also it allows pressure measurements on surfaces where conventional pressure tap technique would be difficult if not virtually impossible, due to various constraints: thin section surfaces, wing-pylon-nacelle junction, stores under military aircraft.. .All aerodynamic surfaces can be potentially considered: wing, HTP, VTP, control surfaces,... on both sides thus providing a global knowledge of the pressure field. At ONERA the research type of work on this test technique is conducted by the Fundamental and Experimental Aerodynamics Department DAFE. The Large Test Facilities Department GMT concentrated its attention, initially, on the evaluation of a commercially available means to use this new technique in order to arrive as early as possible to its application for the industrial type of tests conducted in the ONERA wind tunnels. In the mid 90s, a Russian system became available for evaluation. The evaluation was first conducted in the transonic 1.75x1.75 test section of the S2MA wind tunnel as a part of a cooperation programme between TsAGI and ONERA. Following the first evaluation in 1995, several test campaigns using the PSP technique were run for the benefit of ONERA industrial clients in the transonic or in the supersonic test section of