Experimental and numerical investigations of controlled transition in low-speed free flight

This paper reports on the joint work of several university research groups, where scientists of five German universities tackled the problem of contro lled laminar-turbulent transition on an unswept motor-glider wing with diff erent low disturbance measurement methods on respective wing-gloves as well as with Direct Numerical Simulations. To establish a comparable measuremen t environment for the different measurement methods as well as to facilitat e the comparison between measurement and numerical results, a controlled co ntinuous disturbance wave train excited by a harmonic point source was intr oduced into the boundary-layer flow. A successful comparison between the co ntrolled experiment and simultaneous computations is an essential step towa rds the understanding of more complex transition scenarios like natural tra nsition. The investigation of the downstream development of the three-dimen sional point-source disturbance was the main objective of the mutual resear ch effort. (C) 2001 Editions scientifiques et medicales Elsevier SAS.