Simulation of Wing and Nacelle Stall

Numerical stall simulations are challenging in terms of physical models involved, overall computation effort, and the needed efforts for validation. The present paper describes coordinated, fundamental research into new simulation methodologies and their validation for wing and nacelle stall that also include the effects of atmospheric gusts. The research is carried out by the DFG funded Research Unit FOR 1066, which is composed of German Universities and the German Aerospace Center, DLR. The Research Unit investigates advanced models of turbulence, advanced physics-based gust models, and new numerical approaches for gust simulation. These modeling and computational activities are supplemented by new validation experiments, that aim at providing stall data on wings and engine nacelles with well defined, generic distortions of the onset flow

Numerical Simulations of Streamwise Vortices on a Generic High-Lift Configuration

The results of numerical simulations on a generic high-lift configuration are shown. The high-lift airfoil features a finite slat, where the slat-end creates strong longitudinal vortices interacting with the flow along the suction side. For the simulations, two computational grids with varying density are created. The properties of the grids are presented. The simulations are performed with the DLR TAU-Code at different angles of attack up to stall. The Menter-SST eddy viscosity turbulence model and the JHh-v2 Reynolds-Stress-Model are applied. Two vortices exist at the spanwise end faces of a slat and the corresponding clean-nose, they trail downstream on the suction side of the wing and influence the high-lift behavior of the configuration. A strong interaction between both vortices is observed for higher angles of attack. The behavior of the vortex system and the stall mechanism is characterized. In particular the effect of the turbulence models of different types on the vortex behavior is shown

Experimental and Numerical Analysis of a Streamwise Vortex Downstream of a Delta Wing

The present paper analyzes the vortical flow downstream of a delta wing. The Delta wing is designed to generate a vortex which resembles the vortex of a nacelle strake. The experimental results of stereo-PIV measurements performed at different positions downstream of the delta wing display the streamwise development of the vortex. The distributions of the mean axial and tangential velocity components and Reynolds-stresses characterize the vortex development. In addition, results of numerical simulations with the DLR TAU-code applying the Menter-SST eddy viscosity model and the SSG/LRR-Omega Reynolds-Stress model show the ability of the turbulence models to capture the vortex development. The experimental results indicate a preservation of the vortex strength and structure downstream of the delta wing. The Menter-SST model does not predict this preservation, rather it computes a rapid decay of the vortex strength and an increase of the vortex size. In contrast, the results of the SSG/LRR-Omega model are in good Agreement with the experiments concerning the mean flow development. However, turbulence in the vortex core is underpredicted by both turbulence models

Aircraft and technology for low noise short take-off and landing

This paper discusses characteristic multi-disciplinary issues related to quiet short take-off and landing for civil transport aircraft with a typical short to medium range mission. The work reported here is focussing on the noise aspects and is embedded in the collaborative research centre CRC880 in Braunschweig, Germany. This long term aircraft Research initiative focusses on a new transport aircraft segment for operation on airports with shorter runway length in commercial air transport. This calls for a community-friendly aircraft designed for operations much closer to the home of its passengers than today. This Scenario sets challenging, seemingly contradictory aircraft technology requirements, namely those for extreme lift augmentation at low noise. The Research Centre CRC880 has therefore devised a range of technology projects that aim at significant noise reductions and at the generation of e�cffient and flexible high lift. The research also addresses flight Dynamics of aircraft at takeoff and landing. It is envisaged that in general significant noise reduction -compared to a reference turbofan driven aircraft of year 2000 technology- necessarily requires component noise reduction in combination with a low noise a/c concept. Results are presented from all the acoustics related projects of CRC880 which cover the aeroacoustic simulation of the source noise reduction by flow permeable materials, the characterization, development, manufacturing and operation of (porous) materials especially tailored to aeroacoustics, new UHBR turbofan arrangements for minimum exterior noise due to acoustic shielding as well as the prediction of jet noise vibration excitation of cabin noise by UHBR engines compared to conventional turbofans at cruise