Abstract
Influence of the external disturbances on boundary-layer transition was investigated experimentally in two kinds of 2-D wing model. The first series of experiments are conducted to clarify transition process and the characteristic of instability wave on the NACA0015 wing. It is the first step to examine whether sensitivity of the residual turbulence and acoustic noise to N value e^N method is dependent on instability mechanism. In results, the amplification of the traveling disturbance are observed and its characteristics are measured. The second series of experiments are conducted to clarify the influence of surface roughness on the transition, by applying water-repellent coating to NACA63(3)-018 wing. As a result, surface roughness becomes larger, but the transition location does not move, by applying water-repellent coating. This results suggest that maintenance-free technology of natural laminar flow, which is requested from aircraft manufacturing, can be achieved.
