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Ironside D.J.,Saint Louis University | Bramesfeld G.,Saint Louis University | Schwochow J.,German Aerospace Center | Schwochow J.,Institute of Aeroelasticity
28th AIAA Applied Aerodynamics Conference | Year: 2010

Recent research interests explore the use of the energy present in atmospheric gusts for drag reduction of small and medium sized uninhabited airborne vehicles. Many approaches use active control systems that detect and make use of energy is present in of atmospheric disturbances. A different, passive approach to make use of the energy of atmospheric gusts can be accomplished with an aircraft-wing structure whose structural dynamics are aeroelastically tailored. Previous studies have shown that significant drag reductions, up to 30 percent, are possible even with zero-mass net-motion gusts. However, due to simplified analysis, a detailed investigation is needed to justify these claims. Various responses were analyzed using coupled aerodynamic and structural dynamic simulations in drag reduction verification. The aerodynamic simulation is based on a potential flow model that uses distributed vorticity elements. The structural dynamic simulation uses an explicit finite difference numerical model of the coupled dynamics of the time-dependent Euler-Bernoulli equation for thin beams in non-symmetrical bending and the time-dependent torsion equation for non-circular cross-sections. The aerodynamic model uses distributed vorticity elements that model the bound circulation in a continuous fashion. © 2010 by D. Ironside, G. Bramesfeld, and J. Schwochow. Source

Imiela M.,German Aerospace Center | Imiela M.,Institute of Aerodynamics and Flow Technology | Wienke F.,German Aerospace Center | Wienke F.,Institute of Aeroelasticity | And 8 more authors.
33rd Wind Energy Symposium | Year: 2015

Reliable predictions for wind turbines become more and more difficult with the increase in overall size and weight. On the one hand external factors such as the influence of wind shear become more important for bigger turbines, internal factors such as structural layout and challenges in the manufacturing process need to be addressed on the other hand. Accurate aerodynamic simulations are an essential requirement for further analyses of aeroelastic stability and aeroacoustic footprint. While the calculations in all of these individual disciplines are challenging the combined simulation of all these disciplines, namely the multidisciplinary simulation is a tough but gainful undertaking. This task is being addressed in the DLR project MERWind which will be presented here. The focus of the paper lays on the aerodynamic and aeroelastic simulation of the NREL 5MW wind turbine using high-fidelity methods. © 2015, American Institute of Aeronautics and Astronautics Inc. All rights reserved. Source

Meddaikar Y.M.,Institute of Aeroelasticity | Irisarri F.-X.,ONERA | Abdalla M.M.,Technical University of Delft
Structural and Multidisciplinary Optimization | Year: 2016

This article presents an optimization tool for the stacking sequence design of blended composite structures. Enforcing blending ensures the manufacturability of the optimized laminate. A novel optimization strategy is proposed combining a genetic algorithm (GA) for stacking sequence tables with a multi-point structural approximation using a modified Shepard’s interpolation in stiffness-space. A successive approximation approach is used where the set of design points used to create the structural approximations is successively enriched using the elite of the previous step. Additional improvement in the generality and efficiency of the algorithm is obtained by using load approximations thus enabling the implementation of a wide range of stress-based design criteria. A multi-panel, blended composite problem is used as an application to demonstrate the performance of the developed tool. The optimization is performed with mass as the objective to be minimized, subjected to strength and buckling constraints. The results presented show that completely blended and feasible stacking sequence designs can be obtained, having their structural performance close to the theoretical continuous optimum itself. Additionally, the multi-point Shepard’s approximation shows a considerable saving in computational costs, while the limitations of inexpensive stiffness-matching optimizations are observed. © 2016 Springer-Verlag Berlin Heidelberg Source

Spehr C.,German Aerospace Center | Spehr C.,German Institute of Aerodynamics and Flow Technology | Hennings H.,German Aerospace Center | Hennings H.,Institute of Aeroelasticity | And 7 more authors.
18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference) | Year: 2012

A series of flight tests were carried out in June 2011 with more than 250 sensors in a cabin cross section upstream of the wings. The main purpose of the flight test was to qualify and quantify the main sources of cabin noise as well as the transfer paths to the passenger under real flight condition. The sensor set consists of pressure transducers installed in three dummy windows, accelerometers on the fuselage and the cabin and microphones inside the cabin. While varying the flight conditions by changing flight altitude, thrust and speed the main noise sources were distinguished and qualified. © 2012 by Carsten Spehr. Source

Dillinger J.K.S.,German Aerospace Center | Dillinger J.K.S.,Institute of Aeroelasticity | Klimmek T.,German Aerospace Center | Klimmek T.,Institute of Aeroelasticity | And 3 more authors.
Journal of Aircraft | Year: 2013

The drive for ever more efficient aircraft structures stimulates the research to use the full potential of anisotropy of composite materials. The stiffness optimization of the upper and lower skins of a composite wing is demonstrated in this paper. The wing was optimized taking into consideration the mass, strength, buckling, aerodynamic twist, and aileron effectiveness. The elements of the in-plane and bending stiffness matrices and laminate thicknesses were used as design variables. Static aeroelastic analysis was performed using NASTRAN to find the responses of the structure and their sensitivities to the design variables. The results of aeroelastic finite element analysis were processed to create efficient structural approximations of the responses. The approximations were used by a gradient-based optimizer to update the design variables. The separable and continuous approximations in terms of the design variables allowed for the use of efficient parallel computing strategies, in which single or multimodal objective functions were minimized. The first numerical results for a generic wing confirmed a functional setup for multiload case stiffness optimizations with aeroelastic design responses. Stiffness-optimized unbalanced laminates demonstrated a clear advantage over balanced laminates for mass or aileron effectiveness optimizations, with constraints on strength and buckling. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

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