Laser Doppler Anemometer for In-Flight Velocity Measurements on Airplane Wings

Abstract

The development of laminar wing technology for commercial airplanes requires strategies that combine wind-tunnel investigations with numerical flow computations and in-flight measurements. One strategy is outlined; it is explained that instruments are needed to measure local flow velocities in wind tunnels as well as to carry out free flight experiments. It is shown that laser Doppler anemometry (LDA) is most suited to provide the required local velocity information, but special LDA systems need to be developed. Results of LDA system developments are summarized. This program yielded two optical units suitable for in-flight velocity measurements on airplane wings. Laboratory and free flight measurements were successfully carried out with the LDA systems developed, and a summary of results is presented. Applications to laminar wing design are indicated. Suggestions for further advancements of the LDA systems are presented