APPLICATIONS OF DIFFERENT MEASURING TECHNIQUES FOR TRANSITION DETECTION IN LOW AND HIGH SPEED FLIGHT EXPERIMENTS

摘要

This paper descibes in-flight measurements at low and high speed experiments to investigate laminar-turbulent transition. The low speed experiments were carried out using a laminar wing glove for a sailplane. High speed experiments on an modified A320 HLF Fin were conducted in close collaboration with Airbus. Different surface sensor measuring techniques (piezofoil, surface hot-wires, wall-microphones) were used in low speed experiments. The piezofoil technique was applied in high speed in-flight experiments to prove the operation robustness, the functional capability, durability and reliability under atmospheric conditions in cruise flight of modern airplanes. All measuring techniques were successfully implemented for the particular task and the laminar-turbulent transition was detected with a high degree of certainty. In contrast to the usual pressure-sensitive measuring techniques (piezofoil), the surface hot-wire sensor shows a decreasing sensitivity with increasing speed, but the best signal to noise ratio in low speed experiments. For the high-speed investigations a complete piezofoil sensor was glued on the fin without observing any interference between the boundary layer flow and the sensor foil. Therefore this technique showed the potential to detect transition in the boundary layer under atmospheric conditions especially in high speed investigations.