Advancement of 2D profile testing at high Reynolds number in the cryogenic wind tunnel Cologne

Abstract

The design and optimization of 2D profiles play a decisive role in the enhancement of the overall performance of an aircraft. Though there are a large series of profiles available with detailed test data, for a high performance aircraft the profiles must be specially designed. Thus there is a need for the 2D profile testing in wind tunnels at high Reynolds numbers. In order to meet this need, the cryogenic wind tunnel Cologne (DNW-KKK) has developed the 2D profile measuring technique for cryogenic conditions. In the first 2D test setup the profile is only driven at one end by a servomotor. This can not prevent the profile from twisting under the thermal and aerodynamic load. The 2D support is thus modified from a one motor drive system into a synchronized two motor drive systems. Boundary layer blowing is used in DNW-KKK to control the boundary layer at the intersection areas between the profile and the tunnel walls, so that the flow around the profile is two dimensional. Besides the pressure measurement, infrared thermograph, laser velocimetry and dynamic measurement using kulite have been performed. With these techniques the requirements of 2D measurements can be met. For a better preparation of the profile tests and wall correction in our wind tunnel, we have investigated the characteristics of the profiles with numerical methods before the test. We have computed the polar under the two different far field boundary conditions: solid walls and infinite flow. The difference of these two polar is then the wind tunnel wall effect. We have compared this difference with the effect calculated by our wall correction method. The comparison shows that the wall correction method used is correct. Up to now various 2D profiles, such as laminar, high lift, high speed profiles and profiles for windmills have been tested in DNW-KKK. The repeatability of the measurements is very high.