DLR Contribution to the First High Lift Prediction Workshop

DLR’s contribution to the first AIAA High Lift Prediction Workshop (HiLiftPW-1) covers computations of all three scheduled test cases for the NASA trapezoidal wing in high lift configuration. The DLR finite volume code TAU has been employed as the flow solver. In a standard set-up the one-equation turbulence model of Spalart and Allmaras in the original formulation is used to model effects of turbulence. For selected grids and flow conditions, the k-ω SST model of Menter and a differential Reynolds stress model (SSG/LLR-ω ) developed by DLR have been considered. DLR contributed with two hybrid unstructured grid families to the workshop. The grids have been generated with the grid generation packages Centaur and Solar. A grid family with three Solar grids has been generated and provided to the workshop featuring grids of 12·10^6 , 37·10^6 , and 111·10^6 points for test case 1. In addition, a Solar grid of 37·10^6 points has been provided for test case 2, and a grid of 40·10^6 for the configuration including the slat and flap brackets (test case 3). DLR didn’t succeed in generating a fine-grid with the Centaur package. In order to complete a Centaur grid family with three grid levels an extra-coarse grid has been provided. Thus, the three levels of the Centaur grid family are realized by grids of 13·10^6 , 16·10^6 , and 32·10^6 points. In general a go o d agreement between the experimental evidence and the polar computations on the Solar and Centaur grids is found in terms of forces, moments and wing pressure distributions. The wing tip area with the rearward part of the main wing and the flap represents the most challenging part of the configuration, especially at angles of attack around maximum lift. The deviations between the TAU solutions and the experimental data in this area are only weakly influenced by the different grid topologies or turbulence models used. The influence of the grid resolution of both grid families is comparable, taking into account the different absolute resolution levels of both grid families. Including the slat and flap brackets leads to the expected lift decrease. Concerning the convergence properties, a strong dependence on the numerical start-up procedure has been detected in many of the computations at higher angles of attack

Comparison of the NASA Common Research Model European Transonic Wind Tunnel Test Data to NASA Test Data

Experimental aerodynamic investigations of the NASA Common Research Model have been conducted in the NASA Langley National Transonic Facility, the NASA Ames 11-ft wind tunnel, and the European Transonic Wind Tunnel. In the NASA Ames 11-ft wind tunnel, data have been obtained at only a chord Reynolds number of 5 million for a wing/body/tail = 0 degree incidence configuration. Data have been obtained at chord Reynolds numbers of 5, 19.8 and 30 million for the same configuration in the National Transonic Facility and in the European Transonic Facility. Force and moment, surface pressure, wing bending and twist, and surface flow visualization data were obtained in all three facilities but only the force and moment, surface pressure and wing bending and twist data are presented herein

Experimental Assessment of Wing Lower Surface Buffet Effects Induced by the Installation of a UHBR Nacelle

The installation of large bypass ratio engines on classical under wing configurations may lead to shock/boundary layer interaction on the wing lower surface, limiting the flight envelope in a similar way to classical buffet occurring on the wing suction side at high incidences in transonic flight. In this study, buffet effects on the lower surface of the wing induced by the installation of a Ultra-High-Bypass-Ratio through flow nacelle are assessed by means of wind tunnel testing. Unsteady pressure sensitive paint measurements were used to assess the pressure field on the wing with high temporal and spatial resolution. Strong unsteady shock motion associated with shock induced separation was found on the wing lower surface for various combinations of Mach number, Reynolds number and angle of attack. The wing lower surface buffet effects are found to increase with reducing angle of attack and are present over a wide range of Reynolds numbers. Preliminary spectral analysis suggests an upper limit for the buffet frequency at a Strouhal number of about 0.4

Design of a UHBR Through Flow Nacelle for High Speed Stall Wind Tunnel Investigations

The design of a new through flow nacelle for the Airbus XRF1 wind tunnel model is presented. The nacelle is representative of a modern UHBR turbofan engine for long range transport aircraft and was especially designed to investigate the interaction of buffet phenomena on the wing lower side, pylon and nacelle within the research unit FOR 2895. During the design process the performance of the through flow nacelle was evaluated by performing RANS simulations with the DLR TAU code using Spalart-Allmaras as well as Reynolds- Stress turbulence models. For the initial nacelle design simulations of the isolated nacelle were performed. Having obtained an initial nacelle shape, it was integrated in the XRF1 CAD model. A pylon geometry was designed and a baseline nacelle position and orientation was defined. The numerical simulations proved the configuration with nacelle and pylon shows adequate performance under cruise conditions without exhibiting unusual adverse effects on the aircraft. As intended, significant shock induced separations were observed on the wing lower side inboard of the nacelle for high speed off-design conditions with negative angles of attack allowing the investigation of buffet phenomena. The numerical results were also used to identify suitable locations for the pressure instrumentation on nacelle and pylon for the wind tunnel test at ETW

DLR TAU Simulations for the Third AIAA Sonic Boom Prediction Workshop

The presentation summarizes the DLR contribution to the 3rd AIAA Sonic Boom Prediction Workshop. A grid generation approach using CENTAUR is presented. Near-field simulation results for the jet-plume interaction case and the C608 low boom geometry were presented. Results for both, workshop-provided and CENTAUR-generated grids are compared. A good grid convergence is achieved for fine grids

Experimental Investigation of the DLR-F6 Transport Configuration in the National Transonic Facility

An experimental aerodynamic investigation of the DLR (German Aerospace Center) F6 generic transport configuration has been conducted in the NASA NTF (National Transonic Facility) for CFD validation within the framework of the AIAA Drag Prediction Workshop. Force and moment, surface pressure, model deformation, and surface flow visualization data have been obtained at Reynolds numbers of both 3 million and 5 million. Flow-through nacelles and a side-of-body fairing were also investigated on this wing-body configuration. Reynolds number effects on trailing edge separation have been assessed, and the effectiveness of the side-of-body fairing in eliminating a known region of separated flow has been determined. Data obtained at a Reynolds number of 3 million are presented together for comparison with data from a previous wind tunnel investigation in the ONERA S2MA facility. New surface flow visualization capabilities have also been successfully explored and demonstrated in the NTF for the high pressure and moderately low temperature conditions required in this investigation. Images detailing wing surface flow characteristics are presented

Flight mechanics model for spanwise lift and rolling moment distributions of a segmented active high-lift wing

In this study, the aerodynamics of wings using an active high-lift system are investigated. The target is the flight mechanical description of the spanwise forces and resulting moments and the influence of the active high-lift system to their distribution. The high-lift system is a blown flap system divided into six segments per wing. Each segment is assumed to be individually controlled, so the system shall be used for aircraft control and system failure management. This work presents a flight mechanical sub-model for the simulation of flight dynamics, which has been derived from high-fidelity CFD results. An assessment of single-segment blowing system failures will be presented including recommendations for compensation of either lift or rolling moment loss. For this investigation, the compensation is required to act at the same wing side on which the failure appears. Thus, the potential for an increase of system reliability shall be proven. The results show that less performance investment in terms of pressurized air is necessary to compensate the rolling moment of a failing segment instead of its lift. However, large blowing performance increases for the remaining wing segments that occur for some of the failure cases

Aerodynamic Aspects of the Longitudinal Motion of a High-Lift Aircraft Configuration with Circulation Control

The aim of sub-project C1 of the Collaborative Research Center/Sonderforschungsbereich 880 (SFB 880) is to investigate numerically the flight mechanical characteristics of an aircraft with circulation controlled high-lift devices from an aerodynamic point of view. This paper summarizes the most important aspects of the work done so far. It begins with a basic analysis of the impact of varying blowing coefficients on the aircraft performance based on the wing-body configuration. Furthermore, an overview of the influence of the circulation controlled wing on the aerodynamics of the horizontal tail plane is presented. Eventually, the resulting longitudinal static stability and controllability behavior of the SFB 880’s reference aircraft is discussed. Additionally, the interaction of a circulation controlled wing and the slipstream of a wing mounted turboprop engine is investigated. Besides the studies of the static behavior, first results of the dynamic behavior, specifically the temporal behavior of circulation control after being activated are presented

Aerodynamic assessment of potential rudder force augmentation due to circulation control based on a VTP rudder design for a STOL aircraft

The scope of the paper is to assess the potential of using circulation control at the vertical tail plane in order to increase the maximum rudder side force. Therefore, a numerical study on the rudder design is carried out, consisting of a 2D sensitivity study, an estimation of the 3D forces and moments via lifting line method, and a verification by 3D Reynolds-averaged Navier-Stokes (RANS) simulations. Compared to the baseline rudder, the lifting line method yields a 138% increase of the rudder yawing moment due to the use of circulation control. 3D RANS simulations verify the lifting line results. The deviation between yawing moments from the RANS computations and the lifting line method is less than 11%

Active Flow Separation Control on a High-Lift Wing-Body Configuration - Part 1: Baseline Flow and Constant Blowing

This paper describes the influence of grid resolution and turbulence modeling for a 3D transport aircraft in high lift configuration with massive flap separation. The flap is equipped with spanwise slotted active flow control (AFC) devices to allow studies on active separation control. The effects of constant slotted blowing on the high lift performance are highlighted. Oil flow pictures from a mid-scale experiment in the low speed wind tunnel of Airbus in Bremen (B-LSWT) serve as a validation database for the baseline CFD results. RANS calculations are carried out with and without constant blowing boundary conditions. The baseline flow is also investigated with a time-accurate URANS approach. One of the major outcomes of the AFC study is the demonstration of the feasibility to simulate AFC concepts on a 3D configuration. Constant blowing shows the beneficial effect that separation can largely be suppressed because of the energy added to the flow on the suction side of the flap. This study serves as a preceding validation for the subsequent pulsed blowing approach treated in Part 2