The Cryogenic Ludwieg-Tube Göttingen (KRG) of the German Aerospace Center (DLR)

Abstract

The Cryogenic Ludwieg-Tube Göttingen (KRG) of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) is a Ludwieg-tube type of wind tunnel designed for high Reynolds number research in transonic flow. Temperatures down to 120 K and stagnation pressures up to 1 MPa are realised to achieve Reynolds numbers of up to Re = 60 x 10⁶ (2-D) based on a model chord of 150 mm while providing an exceptionally low turbulence level due to its design.

The Cryogenic Ludwieg-Tube Göttingen (KRG), in conjunction with the European Transonic Windtunnel (ETW), constitutes the exclusive aerodynamic infrastructure in Europe capable of achieving transonic flow at Reynolds numbers representative of full-scale flight conditions for modern transport aircraft. The KRG serves as a cornerstone of contemporary and future aeronautical research into high-Reynolds-number transport aircraft aerodynamics. It provides an economically efficient platform for the maturation of measurement techniques tailored to the rigorous demands of cryogenic test environments. Major research topics focus on drag reduction by laminar-turbulent boundary layer transition control and cavity flows for future aircrafts.

The present paper provides an overview over the Ludwieg-Tube concept and describes the design and operation of the facility as well as the main components with special emphasis on the 2-D adaptive wall test section and the adaptation method. Furthermore, an overview on typical measurement techniques and selected research topics is provided.