Some Aspects of Flow Transition Detection when Flight Testing Carbon Fibre Composite Conventional and Laminar Flow Nacelles

Abstract

In aeronautical substantial improvements in the fields of economy and ecology can be achieved by the application of the laminar flow technology. The basis for a successful application of the laminar flow technology are complementary approaches using numerical and experimental tools. As regards the latter, by conducting flight trials this procedure not only has the advantage of yielding results that relate to a realistic environment in contrast to simulated conditions, as encountered for instance in wind tunnels, but also the Reynolds numbers associated with the flight testing represent realistic values. The report deals with some lessons learned as regards the flow transition detection in the course of flight testing carbon fibre composite conventional and laminar flow nacelles. The flight trials were conducted within the framework of a European collaborative programme. Particular aspects covered are the influences of environmental phenomena and of the engine nacelle structure regarding the interpretation of the nacelle infra-red images and of the nacelle surface temperature measurements, both with reference to determine the location of the flow transition front on the nacelles.