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Berlin, Germany

Isele T.,Technical UniversityBerlin | Hartung B.,Technical UniversityBerlin | Hovel P.,Technical UniversityBerlin | Hovel P.,Humboldt University of Berlin | Scholl E.,Technical UniversityBerlin
European Physical Journal B | Year: 2015

We examine traveling-wave solutions on a regular ring network with one additionallong-range link that spans a distance d. The nodes obey the FitzHugh-Nagumo kinetics inthe excitable regime. The additional shortcut induces a plethora of spatio-temporalbehavior that is not present without it. We describe the underlying mechanisms fordifferent types of patterns: propagation failure, period decreasing, bistability, shortcutblocking and period multiplication. For this purpose, we investigate the dependence ond, thenetwork size, the coupling range in the original ring and the global coupling strength andpresent a phase diagram summarizing the different scenarios. Furthermore, we discuss thescaling behavior of the critical distance by analytical means and address the connectionto spatially continuous excitable media. © 2015, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source


Zander V.,Technical UniversityBerlin | Nitsche W.,Technical UniversityBerlin
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy | Year: 2013

This paper presents detailed flow-field measurements for a compressor cascade equipped with synthetic jet actuators for active flow control. The synthetic jets are mounted on the cascade sidewall and the suction side surface of the blade to reduce the total pressure loss caused by strong secondary flow structures developing in the passage. There are certain articles reporting that synthetic jets are well suited for flow control applications even in axial compressors and cascades. Most of them are focused on the parameter variation to optimize the efficiency of the control approach, still very little is known on the interaction of the synthetic jet actuators with the flow field. Detailed x-wire and pressure measurements were conducted to understand how synthetic jets influence the flow field and what causes the significant loss reduction in the cascade wake. It seems that the added momentum is not the key parameter for flow control with synthetic jets. In fact, the high mixing and the unsteadiness of the jets seem to amplify existing velocity fluctuations in the flow field. These increased fluctuations result in a shift of the shear layer between the flow separation and the surrounding flow, and thus in a dethrottling of the compressor cascade. Together with the increased mixing, loss reductions of approximately 10% can be reached using synthetic jet actuators. © IMechE 2013. Source


Lindow K.,Technical UniversityBerlin | Woll R.,Technical UniversityBerlin | Woll R.,Fraunhofer Institute for Production Systems and Design Technology | Stark R.,Technical UniversityBerlin | Stark R.,Fraunhofer Institute for Production Systems and Design Technology
Leveraging Technology for a Sustainable World - Proceedings of the 19th CIRP Conference on Life Cycle Engineering | Year: 2012

The paper describes a framework for the implementation of sustainable aspects into engineering design. The focus is on qualifying and enabling engineers in order to develop sustainable products thus a bottom-up approach is presented. The approach describes how the engineer can get aware of sustainable product design. So-called contextual sustainability behaviors are suggested. Since a product cannot meet all sustainable demands at a time, the proposed contextual sustainability areas will help to trade-off the over-constraint design solution space. A case study shows how the contextual sustainability areas are applied to a specific product. Additionally, an IT supported approach is introduced. The framework was developed for research community and is now heading towards industrial testing. Source

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