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Barth T.,Braunschweig Institute of Technology | Scholz P.,Braunschweig Institute of Technology | Scholz P.,Institute of Fluid Mechanics | Wierach P.,German Aerospace Center | Wierach P.,German Institute of Composite Structures and Adaptive Systems
AIAA Journal

This paper describes a study of dynamical vane vortex generators in a flow over a flat plate. Fluidic vortex generators are more effective when operated dynamically. Thus, it is the aim of this study to find out whether mechanical vortex generators are also superior under dynamic operating conditions. The motion of the vortex generators is generated by piezoceramic actuators constructed in a bimorph configuration, which consists of a carbon-fiber bar covered with piezoceramic face actuators. The actuators exploit the longitudinal piezoelectric effect (d33 effect), they are operated in resonance to reach the required displacement and generate a sinusoidal motion of the vortex generators. Vortex generators and actuators were integrated into a flat plate in a low-speed wind tunnel. A stereo particle image velocimetry system was used to record phase-locked flowfields that were analyzed using vortex classification methods. It was found that the transient development of the vortex core position and circulation is very different from that of static vanes. While vortices from static vortex generators are able to survive over a considerable distance, the vortices from dynamically driven ones decay faster. It is argued that the dynamic vortices have a greater ability to reorganize the momentum in the turbulent boundary layer. Copyright © 2010 by Peter Scholz. Source

Willberg C.,German Aerospace Center | Duczek S.,Otto Von Guericke University of Magdeburg | Vivar-Perez J.M.,German Institute of Composite Structures and Adaptive Systems | Ahmad Z.A.B.,University of Technology Malaysia
Applied Mechanics Reviews

This paper reviews the state-of-the-art in numerical wave propagation analysis. The main focus in that regard is on guided wave-based structural health monitoring (SHM) applications. A brief introduction to SHM and SHM-related problems is given, and various numerical methods are then discussed and assessed with respect to their capability of simulating guided wave propagation phenomena. A detailed evaluation of the following methods is compiled: (i) analytical methods, (ii) semi-analytical methods, (iii) the local interaction simulation approach (LISA), (iv) finite element methods (FEMs), and (v) miscellaneous methods such as mass-spring lattice models (MSLMs), boundary element methods (BEMs), and fictitious domain methods. In the framework of the FEM, both time and frequency domain approaches are covered, and the advantages of using high order shape functions are also examined. Copyright © 2015 by ASME. Source

Ucan H.,German Institute of Composite Structures and Adaptive Systems
JEC Composites Magazine

Given the demands of the aviation industry, the challenges of the carbon fibre reinforced plastics (CFRP) industry cannot be met with the current technology. This paper introduces a new concept to improve the autodave process in order to achieve high part quality and productivity at low part cost and with low scrap rates. Source

Hoffmann F.,German Aerospace Center | Keimer R.,German Institute of Composite Structures and Adaptive Systems | Riemenschneider J.,German Institute of Composite Structures and Adaptive Systems
CEAS Aeronautical Journal

DLR has been researching on active twist rotor blade control for at least 15 years now. This research work included the design and manufacturing of model rotor blades within the blade skin integrated actuators. As a main subject, numerical benefit studies with respect to rotor noise, vibration, and performance were carried out with DLR’s rotor simulation code S4. Since this simulation code is based on a modal synthesis, it uses the natural blade frequencies and mode shapes to model the blade dynamics. Both, natural blade frequencies and mode shapes, are computed in advance employing a finite element beam model of the blade. Each beam element possesses certain structural properties that are derived from an ANSYS model for certain cross sections of the blade. Since model rotor blades are built for wind tunnel testing, they are highly instrumented with sensors and therefore vary in their structural properties along span. Modifications in the structural properties due to the instrumentation are not included in the ANSYS model. However, to account for these variations, two experimental methods have been developed. They allow the determination of the real values for the most important structural blade properties such that the structural blade model is improved. The paper describes the experimental methods, as well as the development of an advanced structural blade model for rotor simulation purposes. It shows a validation of the structural blade model based on the measured non-rotating and rotating frequencies. © 2015, Deutsches Zentrum für Luft- und Raumfahrt e.V. Source

Monner H.P.,German Aerospace Center | Riemenschneider J.,German Institute of Composite Structures and Adaptive Systems | Kintscher M.,German Institute of Composite Structures and Adaptive Systems
Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

The future generation of high lift devices for transport aircrafts has to contribute to the reduction of noise during landing and a reduction of drag during cruise flight. Also it has to be compatible with affords for natural laminar flow on the wing. A smart gapless droop nose would be an alternative to today's slats and promises to contribute to those goals. A consortium of Airbus, EADS-IW, CASSIDIAN and DLR developed such a smart leading edge in the framework of the fourth German national research program in aeronautics. This paper describes a 1:1 3D fiber reinforced flexible smart droop nose and its ground test. The results of these tests will finally be compared with the results of the finite element simulation. © 2012 AIAA. Source

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