Systematic Study on the Fluid Dynamical Behaviour of Streamwise and Laterally Inclined Jets in Crossflow

ABSTRACT The design of discrete film cooling holes for gas turbine airfoil applications is governed by a number of parameters influencing both their aerodynamic and thermal behaviour. This numerical and experimental study focuses on the marked differences between film cooling holes with combined streamwise and lateral inclination and film cooling holes with streamwise inclination only. The variation in the blowing angle was chosen on a newly dermed and physically motivated basis. High resolution low speed experiments on a large scale turbine airfoil gave insights particularly into the intensified mixing process with lateral ejection. The extensive computational study is performed with the aid of a 3D blockstructured Navier-Stokes solver incorporating a low-Reynolds-number k-e turbulence model. Special attention is paid to mesh generation as a precondition for accurate highresolution results. The downstream temperature fields of the jets show reduced spanwise variations with increasing lateral blowing angle; these variations are quantified for a comprehensive variety of configurations in terms of adiabatic film cooling effectiveness

The effect of functional splinting on mild dysplastic hips after walking onset

BACKGROUND: For treatment of Graf class IIb dysplastic hips at walking onset a treatment concept with abduction splints allowing patterns as walking and crawling under constant abduction control was investigated. However, as the splint still incapacitates child movements the research question remains whether the physiologically progressing maturation of hips can be significantly altered using such abduction splints for walking children. METHODS: Of 106 children showing late hip dysplasia, 68 children treated with the Hoffman-Daimler (HD-splint) abduction splint were compared with 38 children with neglect of the abduction treatment in this retrospective study. Radiographic analyses were performed measuring the development of the age dependent acetabular angle. RESULTS: The regression analysis for splint treatment showed a significant linear regression for both splint treatment and no splint treatment group (r(2 )= 0,31 respectively r(2 )= 0,33). No statistical difference between both treatment groups was apparent. CONCLUSION: Considering the characteristics of this study, there seems to be no strong rationale supporting the use of an abduction device in growing children. As no significant difference between treatment groups is apparent, a future controlled prospective study on splinting effects can be considered ethically allowed

The role of hydrogen and fuel cells in the global energy system

Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarb onisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, h eat, industry, transport and energy storage in a low - carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain nic hes such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225,000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium - term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world

Metallisierung von HT-Polymerwerkstoffen durch Einsatz oekologisch orientierter Verfahrenstechniken. Teilvorhaben: Kombinierte chemische und physikalische Verfahren zur Metallisierung von Polymerwerkstoffen Abschlussbericht

Preconditioning methods like chemical etching of standard polymers like ABS are widely used in the industry to provide peeling strengths of more than 1.0 N/mm for copper layers of 30 #mu#m thickness. Chromic acid methods for preconditioning polymers [e.g. polyethersulphone (PES)] must be substituted by ecologically important methods based on chromium free, more environmentally compatible substances. This fact was an essential motivation for investigating the influences of different wet chemical preconditioning methods on the adhesion mechanisms of chemically and galvanically deposited metal layers as well on the above mentioned as on some other filler containing polymers like liquid crystal polymers (LCP), polyphenylenesulfide (PPS), polybutylene-terephthalate (PBT), polyphthalamide (PPA), or polyamide PA4.6. After cleansing, annealing, and wet chemical preconditioning the polymer surfaces were catalytically activated by a tin chloride / palladium chloride process. Copper or nickel phosphorous films of different thicknesses were electrolessly (chemically) plated from common autocatalytically working baths. For investigations on long-time adhesion and on thermal ageing of the polymer-copper or -nickel phosphorous layer systems, the ground layers of both processes were electrolytically reinforced with Cu from a common copper sulfate / sulfuric acid bath up to 30 #mu#m. The adhesion was controlled by a peel test with 1 mm wide ribbons. As shown in the study, the filled polymers can be preconditioned with ecological wet chemical processes to get such a surface quality that well adherent metal layers can be produced by chemical (electroless) and electrolytic plating. Practical tests on the metallized polymers like ageing at 150 C... 230 C or treatment with boiling water could demonstrate the fulfilling of the requirements on electronic packaging in view of soldering processes as well as of high temperatures during practical use. (orig.)SIGLEAvailable from TIB Hannover: F98B821+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Multifunktionale Mikrowellen- und Millimeterwellenmodule. Teilvorhaben: Funktionelle Beschichtungen Abschlussbericht

SIGLEAvailable from TIB Hannover: F00B1178+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Erforschung von Verfahrenskombinationen zur Erzeugung elektromagnetisch schirmender Schichtsysteme Abschlussbericht

Available from TIB Hannover: F95B739+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Auslegung einer robusten Kaskadenregelung

A number of methods is available for the design of complete state feedback systems. The method for ''designing a robust cascade control'' defined in this report also belongs to the group of those methods which indicate a possible dimensioning for a complete state feedback. The design methodology described in this report is based on observations in the domain of frequency. Real boundary conditions (e.g. given actuating dynamics) as given for each practical controller design are taken into account by this method in a very simple way as early as in the control approach. In particular this design method permits to recognize for which controlled system favorable or unfavorable conditions for robust control are given. As the dynamic behavior of many controlled systems can be freely designed within certain limits (e.g. center-of-pressure or center-of-gravity movements on aircraft or missiles), it is appropriate to establish those parameters of a controlled system, which can be influenced by corresponding design measures, so that this permits a simplified controller design and robust control. Specifications for a favorable parameter design can be read immediately from the controller design. (orig.)Available from TIB Hannover: RR 5368(1685) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

VERBMOBIL: Entwicklung eines mobilen Systems zur Uebersetzung von Verhandlungsdialogen in face-to-face Situationen Abschlussbericht

Available from TIB Hannover: F97B1304+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman