MATHEMATICAL-ANALYSIS OF AREAS OF FLOW SU BJECTED TO FRICTION

The Basics of the description of wave packets generated by localized d isturbances in an unstable three-dimensional compressible flow are pre sented. The classification into convectively and absolutely unstable b ehaviour is explained as well as the mathematical criteria (collision- , saddlepoint criterion) for the distinction of these two phenomena. T he worked out stability analyses of crossflow- and Tollmien-Schlichtin g instability on a swept wing both show convectively unstable behaviou r. The amplification of the crossflow instability reacts strongly upon small changes in si veep angle near a wing sweep of about 20 degrees.