Experimental and numerical studies of the low speed wind tunnel DNW-NWB’s open test section towards an aeroacoustic facility

Abstract

This paper presents results of experimental and numerical investigations performed in the open-jet of the low speed atmospheric wind tunnel DNW-NWB prior the revision to accommodate a high-performance aeroacoustic test section. The investigations aim to assess the accuracy of the computations for open tunnel test sections and include a basic study of the empty tunnel as well as a study of a complex flow topology, the full 3D high-lift model of Do728 in landing configuration. The basic study addresses aerodynamic measurements of the open-jet flow in the empty tunnel which include pressure distributions along the tunnel axis and in cut planes downstream the rectangular nozzle as well as limited hot-wire measurements for the shear layers. The steady RANS simulations have a computational domain restricted to settling chamber, nozzle, test section and collecting system and are in very good agreement with the experimental findings. The pressure along the tunnel axis which has a bath-tube-shape-like with gradients after the nozzle and before the collector has still place for aerodynamic improvements. The investigations with the 3D high-lift Do728 model are devoted to cross-comparisons with the aerodynamic closed test section setup and to a better understanding of the flow deviations of the open-jet at high angles of attack and high lift force. It is shown that the flow is still well captured by the collecting system and that the numerics predict well the flow physics prior to maximum lift. The implications of this work are discussed related to the latter modification of the DNW-NWB facility to allow accurate aerocoustic testing as well as towards the optimization of the collecting system. First results of the ongoing work to optimize the collector’s geometry are presented.