Influence of pressure driven secondary flows on the behavior of turbofan forced mixers

A finite difference procedure was developed to analyze the three dimensional subsonic turbulent flows in turbofan forced mixer nozzles. The method is based on a decomposition of the velocity field into primary and secondary flow components which are determined by solution of the equations governing primary momentum, secondary vorticity, thermal energy, and continuity. Experimentally, a strong secondary flow pattern was identified which is associated with the radial inflow and outflow characteristics of the core and fan streams and forms a very strong vortex system aligned with the radial interface between the core and fan regions. A procedure was developed to generate a similar generic secondary flow pattern in terms of two constants representing the average radial outflow or inflow in the core and fan streams as a percentage of the local streamwise velocity. This description of the initial secondary flow gave excellent agreement with experimental data. By identifying the nature of large scale secondary flow structure and associating it with characteristic mixer nozzle behavior, it is felt that the cause and effect relationship between lobe design and nozzle performance can be understood

Inlet-engine matching for SCAR including application of a bicone variable geometry inlet

Airflow characteristics of variable cycle engines (VCE) designed for Mach 2.32 can have transonic airflow requirements as high as 1.6 times the cruise airflow. This is a formidable requirement for conventional, high performance, axisymmetric, translating centerbody mixed compression inlets. An alternate inlet is defined, where the second cone of a two cone center body collapses to the initial cone angle to provide a large off-design airflow capability, and incorporates modest centerbody translation to minimize spillage drag. Estimates of transonic spillage drag are competitive with those of conventional translating centerbody inlets. The inlet's cruise performance exhibits very low bleed requirements with good recovery and high angle of attack capability

Computation of three-dimensional flow in turbofan mixers and comparison with experimental data

A three dimensional, viscous computer code was used to calculate the mixing downstream of a typical turbofan mixer geometry. Experimental data obtained using pressure and temperature rakes at the lobe and nozzle exit stations were used to validate the computer results. The relative importance of turbulence in the mixing phenomenon as compared with the streamwise vorticity set up by the secondary flows was determined. The observations suggest that the generation of streamwise vorticity plays a significant role in determining the temperature distribution at the nozzle exit plane

Konstruktivistische Ansätze in der Psychologie

Constructivistic approaches - except the radical constructivism - are prevalent in psychology, especially if approaches are included which apply core characteristics of constructivistic theories and employ constructivistic concepts and principles, e. g. concept metaphors, cognitive structure or self organisation in connectionistic networks. Some of these approaches do not explicitly regard themselves as constructivistic. These concepts are especially significant for the analysis of knowledge acquisition and knowledge construction but also for text comprehension, cognitive development, and social attitude. Constructivism has been specifically influential for the clarification of the relationship between construction and instruction concerning knowledge acquisition. The moderate constructivism offers an opportunity to get to an important methodological orientation of psychological research in this field.Konstruktivistische Ansätze sind - mit Ausnahme des radikalen Konstruktivismus - in der Psychologie weit verbreitet, insbesondere dann, wenn man auch solche Ansätze mit einbezieht, die sich zwar selbst nicht ausdrücklich als solche bezeichnen, aber Kernmerkmale konstruktivistischer Theorien verwenden und konstruktivistische Konzepte und Prinzipien einsetzen, z. B. Konzept-Metaphern, kognitive Schemata oder Selbstorganisation in konnektionistischen Netzen. Diese Konzepte sind vor allem bei der Untersuchung von Wissenserwerb und Wissenskonstruktion, aber auch für das Verständnis von Texten, für die kognitive Entwicklung und soziale Einstellungen bedeutsam. Als besonders einflussreich erwies sich der Konstruktivismus bei der Klärung des Verhältnisses von Konstruktion und Instruktion beim Wissenserwerb. Der moderate Konstruktivismus bietet eine gute Chance, zu einer wichtigen methodologischen Orientierung psychologischer Forschung in diesen Bereichen zu werden

Methodologie und Empirie zum situierten Lernen

Auch neue theoretische Ansätze müssen sich in der empirischen Forschung bewähren, zumal dann, wenn sie aus der Kritik an etablierten Theorien hervorgegangen sind; dies gilt auch für Ansätze zum situierten Lernen. In diesem Beitrag werden zuerst einige wichtige Merkmale dieser Ansätze vorgestellt, um danach die wichtigsten Studien und deren Designs zu diskutieren. Nach einer ersten, überwiegend ethnomethodologisch orientierten Phase zeichnet sich die gegenwärtige zweite Forschungsphase durch eine Zuwendung zur Untersuchung der kollaborativen Lernkultur und des in dieser verteilten gemeinsamen und individuell distribuierten Wissens aus, mit komplexeren Designs und Feldexperimenten, die zumeist am Prinzip der ökologischen Validität orientiert sind. Die vorgestellten Arbeiten von fünf Forschergruppen verweisen auf eine veränderte Methodologie, die als interaktive oder als integrative Methodologie bezeichnet wird. Zum Schluss werden mögliche Konsequenzen für die Technologie und Philosophie der Bildung angesprochen. (DIPF/Orig.)If new theoretical approaches emerge from criticism of established theories, they have to prove reasonable in the framework of empirical research projects. This is also true for approaches of contextual learning. In this contribution, characteristic features of contextual learning approaches will be described. In addition, the most important research surveys and their designs will be discussed. Following the first predominantly ethno-methodological phase, current research focuses on the investigation of the collaborative culture of learning, analyzing both shared and individual knowledge. At this stage, research is mainly based on the principle of ecological validity, implemented by means of complex designs and field experiments. The presented surveys of five research groups show a change in methodology that is called interactive or integrative methodology. Finally, this contribution refers to possible consequences for educational philosophy and technology. (DIPF/Orig.

Hot-flow tests of a series of 10-percent-scale turbofan forced mixing nozzles

An approximately 1/10-scale model of a mixed-flow exhaust system was tested in a static facility with fully simulated hot-flow cruise and takeoff conditions. Nine mixer geometries with 12 to 24 lobes were tested. The areas of the core and fan stream were held constant to maintain a bypass ratio of approximately 5. The research results presented in this report were obtained as part of a program directed toward developing an improved mixer design methodology by using a combined analytical and experimental approach. The effects of lobe spacing, lobe penetration, lobe-to-centerbody gap, lobe contour, and scalloping of the radial side walls were investigated. Test measurements included total pressure and temperature surveys, flow angularity surveys, and wall and centerbody surface static pressure measurements. Contour plots at various stations in the mixing region are presented to show the mixing effectiveness for the various lobe geometries

Führungsfrauen im Management: Erfolgsmerkmale und Barrieren ihrer Berufslaufbahn

Despite increased efforts in politics and business to promote equal opportunities, women remain underrepresented in management positions within large German companies. This article summarizes selected results from empirical studies about agency traits of women in management positions. The study was based on 100 interviews with successful female business managers. The study investigated the professional development barriers which confront women in managerial positions and the resources which help them meet their professional challenges. It was revealed that the majority of women in the survey had experienced gender stereotyping. On the other hand, internal resouces helped women move up the career ladder (high self-efficacy expectations, active coping strategies and a mix of masculine and feminine characteristics) as well as active networking and social support.Trotz verstärkter Gleichstellungsbemühungen von Politik und Wirtschaft sind Frauen in Führungspositionen deutscher Großunternehmen unterrepräsentiert. Der vorliegende Beitrag fasst ausgewählte Ergebnisse einer empirischen Untersuchung über agency traits von Frauen in Führungspositionen zusammen. Grundlage der Studie waren 100 Interviews mit erfolgreichen Managerinnen aus der Wirtschaft. Dabei wurde untersucht, mit welchen Barrieren sich Führungsfrauen in ihrer Berufslaufbahn konfrontiert sehen und welche Ressourcen sie dabei unterstützen, um ihre beruflichen Herausforderungen zu meistern. Es hat sich gezeigt, dass der Großteil der befragten Frauen Geschlechtsrollen-Stereotypisierung erlebt hat. Aufstiegsfördernd hingegen waren für die Frauen internale Ressourcen (hohe Selbstwirksamkeits-Erwartungen, aktive Copingstrategien und ein Mix maskuliner und femininer Eigenschaften) sowie eine aktive Netzwerkpartizipation und soziale Unterstützung

The acquisition of knowledge from a constructivist perspective

Die gegenwärtige Konstruktivismus-Diskussion bietet in bezug auf den Wissenserwerb ein uneinheitliches und verwirrendes Bild. Aus diesem Grund werden drei Diskussionslinien in diesem Beitrag herausgearbeitet. Ausgehend von Fragen nach der Objektivität des Wissens und dessen Verhältnis zur Welt, nach der theoretischen Modellierung des Wissens, seiner kontextuellen und kulturellen Einbettung und schließlich nach den Möglichkeiten der Förderung des Wissenserwerbs werden drei Varianten unterschieden:(1) Konstruktivismus als Erkenntnis- und Wissenschaftstheorie; (2) "Neuer" Konstruktivismus in der Soziologie, Kognitionswissenschaft und Psychologie; (3) konstruktivistische Ansätze in der Instruktionspsychologie und empirischen Pädagogik. Abschließend werden Schlußfolgerungen für die Psychologie des Wissenserwerbs gezogen. (DIPF/Orig.)As regards knowledge acquisition, the present discussion on constructivism is marked by a confusing diversity. Therefore, the authors attempt to identify three distinct lines of discussion. Based on questions concerning the objectivity of knowledge and its relation to the universe, the theoretical modeling of knowledge, its contextual and cultural embedding and, finally, possibilities of promoting knowledge acquisition, three different approaches are distinguished: (1) constructivism as epistemology and theory of science; (2) "new" constructivism in the fields of sociology, cognitive science, and psychology; and (3) constructivist approaches in educational psychology and empirical pedagogics. Finally, consequences for the psychology of knowledge acquisition are drawn. (DIPF/Orig.

International Systems Integration on the International Space Station

Over the next few months, the International Space Station (ISS), and human spaceflight in general, will undergo momentous change. The European Columbus and Japanese Kibo Laboratories will be added to the station joining U.S. and Russian elements already on orbit. Columbus, Jules Vernes Automated Transfer Vehicle (ATV) and Kibo Control Centers will soon be joining control centers in the US and Russia in coordinating ISS operations and research. The Canadian Special Purpose Dexterous Manipulator (SPDM) will be performing extra vehicular activities that previously only astronauts on EVA could do, but remotely and with increased safety. This paper will address the integration of these international elements and operations into the ISS, both from hardware and human perspectives. Interoperability of on-orbit systems and ground control centers and their human operators from Europe, Japan, Canada, Russia and the U.S. pose significant and unique challenges. Coordination of logistical support and transportation of crews and cargo is also a major challenge. As we venture out into the cosmos and inhabit the Moon and other planets, it's the systems and operational experience and partnership development on ISS, humanity's orbiting outpost that is making these journeys possible