Active Flow Control at Low Reynolds Numbers by Periodic Airfoil Morphing

This paper investigates the application of a periodically deforming airfoil surface for the purpose of flow control at low Reynolds numbers. A physical model has been fabricated by bonding Macro Fiber Composite (MFC) actuators to the underside of a NACA 4415’s suction surface. The results presented build on work by Jones et al.1 First, the behavior of the surface when actuated at a range frequencies is investigated through a combination of photogrammetric and laser sensor measurements. Second, the aerodynamic performance of this novel flow control technique is presented. It is shown that when the actuation frequency ‘locks-in’ to the surface motion significant improvements in performance are observed in a flight regime notorious for poor airfoil behavior

Die genossenschaftliche Initiative: Ein Baustein der Europäischen Wirtschaft

Kooperationen gewinnen für die Organisation der unternehmerischen Tätigkeit immer stärker an Bedeutung. Hinter dieser einzelwirtschaftlichen Reaktion auf eine herausfordernde Umwelt steht der Wunsch, wettbewerbsfähig zu bleiben oder zu werden. Die Mechanismen, über die Kooperationen dazu beitragen können, sind heute weitgehend erforscht. Können Kooperationen aber auch die Verwirklichung des europäischen Binnenmarktes unterstützen? Dieser Frage geht Jacques Santer, Präsident der Europäischen Kommission von 1995 bis 1999 und über viele Jahre Mitglied des Europäischen Parlaments, in seinem Festvortrag anlässlich der Eröffnung der Internationalen Genossenschaftswissenschaftlichen Tagung 2004 an der Universität Münster nach, der diesem IfG-Arbeitspapier zu Grunde liegt. Jacques Santer zeigt eindrucksvoll, dass Kooperationen kein neues Phänomen sind, sondern dass diese schon in der Hanse Vorreiter der politischen Integration und eine Quelle für wirtschaftlichen Wohlstand waren. Er stellt fest, dass heute Kooperationen gerade für kleine und mittelständische Unternehmen ein geeignetes Mittel sind, um im Konzert der Großen zu bestehen. Sie können dazu beitragen, eine nachhaltige wirtschaftliche Basis aufzubauen und unternehmerische Selbständigkeit zu ermöglichen. Damit können sie zugleich auch einer Intensivierung des Handels und Leistungsaustausches dienen und somit die wirtschaftliche Integration der EU vertiefen: ein Baustein für die europäische Wirtschaft

On orbit validation of solar sailing control laws with thin-film spacecraft

Many innovative approaches to solar sail mission and trajectory design have been proposed over the years, but very few ever have the opportunity to be validated on orbit with real spacecraft. Thin- Film Spacecraft/Lander/Rovers (TF-SL Rs) are a new class of very low cost, low mass space vehicle which are ideal for inexpensively and quickly testing in flight new approaches to solar sailing. This paper describes using TF- SLR based micro solar sails to implement a generic solar sail test bed on orbit. TF -SLRs are high area- to-mass ratio (A/m) spacecraft developed for very low cost consumer and scientific deep space missions. Typically based on a 5 μm or thinner metalised substrate, they include an integrated avionics and payload system -on-chip (SoC) die bonded to the substrate with passive components and solar cells printed or deposited by Metal Organic Chemical Vapour Deposition (MOCVD). The avionics include UHF/S- band transceivers, processors, storage, sensors and attitude control provided by integrated magnetorquers and reflectivity control devices. Resulting spacecraft have a typical thickness of less than 50 μm, are 80 mm in diameter, and have a mass of less than 100 mg resulting in sail loads of less than 20 g/m 2 . TF -SLRs are currently designed for direct dispensing in swarms from free flying 0.5U Interplanetary CubeSats or dispensers attached to launch vehicles. Larger 160 mm, 320 mm and 640 mm diameter TF -SLRs utilizing a CubeSat compatible TWIST deployment mechanism that maintains the high A/m ratio are also under development. We are developing a mission to demonstrate the utility of these devices as a test bed for experimenting with a variety of mission designs and control laws. Batches of up to one hundred TF- SLRs will be released on earth escape trajectories, with each batch executing a heterogeneous or homogenous mixture of control laws and experiments. Up to four releases at different points in orbit are currently envisaged with experiments currently being studied in MATLAB and GMA T including managing the rate of separation of individual spacecraft, station keeping and single deployment/substantially divergent trajectory development. It is also hoped to be able to demonstrate uploading new experiment designs while in orbit and to make this capability available to researchers around the world. A suitable earth escape mission is currently being sought and it is hoped the test bed could be on orbit in 2017/18

Concept and Design of a Multistable Plate Structure

A concept is presented for a compliant plate structure that deforms elastically into a variety of cylindrical shapes and is able to maintain such shapes due to the presence of bistable components within the structure. The whole structure may be fabricated as a monolithic entity using low-cost manufacturing techniques such as injection molding. The key steps in the analysis of this novel concept are presented, and a functional model is designed and constructed to demonstrate the concept and validate the analysis

Evaluation of the MERIS aerosol product over land with AERONET

The Medium Resolution Imaging Spectrometer (MERIS) launched in February 2002 on-board the ENVISAT spacecraft is making global observations of top-of-atmosphere (TOA) radiances. Aerosol optical properties are retrieved over land using Look-Up Table (LUT) based algorithm and surface reflectances in the blue and the red spectral regions. We compared instantaneous aerosol optical thicknesses retrieved by MERIS in the blue and the red at locations containing sites within the Aerosol Robotic Network (AERONET). Between 2002 and 2005, a set of 500 MERIS images were used in this study. The result shows that, over land, MERIS aerosol optical thicknesses are well retrieved in the blue and poorly retrieved in the red, leading to an underestimation of the Angstrom coefficient. Correlations are improved by applying a simple criterion to avoid scenes probably contaminated by thin clouds. To investigate the weakness of the MERIS algorithm, ground-based radiometer measurements have been used in order to retrieve new aerosol models, based on their Inherent Optical Properties (IOP). These new aerosol models slightly improve the correlation, but the main problem of the MERIS aerosol product over land can be attributed to the surface reflectance model in the red

Wind Tunnel Experiments with Flexible Plates in Transonic Flows

The evolution of adaptive shock control bump (SCB) design has seen the system flexibility increase to a point where the aerodynamic loading can affect the deformation of the plate. By studying the effects of a flexible plate subject to transonic flow the fluid structure interaction can be investigated. In this study an array of thin plates (0.4 and 0.6 mm) with different aspect ratios (1 and 1.33) are exposed to a Mach 1.4 normal shockwave. PIV is used in combination with Schlieren imaging to provide a detailed view of the flow curvature surrounding the plate as well as the global shock structure. A technique that extracts the plate deformation from the PIV images is also presented which provides fluid and structural information for each test. The relationship between plate and flow angle is discussed as well as the effect of plate stiffness and free stream influence of each plate configuration

Estimation of spatially correlated random scaling factors based on Markov random field priors

Multiplicative random effects allow for cluster-specific scaling of covariate effects. In many applications with spatial clustering, however, the random effects additionally show some geographical pattern, which usually can not sufficiently be captured with existing estimation techniques. Relying on Markov random fields, we present a fully Bayesian inference procedure for spatially correlated scaling factors. The estimation is based on highly efficient Markov Chain Monte Carlo (MCMC) algorithms and is smoothly incorporated into the framework of distributional regression. We run a comprehensive simulation study for different response distributions to examine the statistical properties of our approach. We also compare our results to those of a general estimation procedure for independent random scaling factors. Furthermore, we apply the method to German real estate data and show that exploiting the spatial correlation of the scaling factors further improves the performance of the model