Experimental Investigations on a Suction Airfoil for Sailplanes

Kurzfassung

It is known from ELFIN-experiments that in conjunction with suction some strange phenomena occur, mainly the rise of wedges of undefined origin. One approach to cover these problems is to exclude possible causes step by step. The present step dealt only with Tollmien-Schlichting instability. The main result was that boundary layer behaved quite normal, no wedges were observed. Full laminar flow to the trailing edge was present only on the lower side and at lower Reynolds-numbers. Experiment and calculation are compared, apparently calculated suction is too low, but even with higher suction only extended laminar flow is obtained but not full. This leads to the assumption that laminar flow behind suction remains somewhat "contaminated" withTollmien-Schlichting waves.