Vortex model of the aerodynamic wake of airborne wind energy systems

Understanding and modeling the aerodynamic wake of airborne wind energy systems (AWESs) is crucial for estimating the performance and defining the design of such systems, as tight trajectories increase induced velocities and thus decrease the available power, while unnecessarily large trajectories increase power losses due to the gravitational potential energy exchange. The aerodynamic wake of crosswind AWESs flying circular trajectories is studied here with vortex methods. The velocities induced at the AWES from a generic helicoidal vortex filament, trailed by a position on the AWES wing, are modeled with an expression for the near vortex filament and one for the far vortex filament. The near vortex filament is modeled as the first half rotation of the helicoidal filament, with its axial component being neglected. The induced drag due to the near wake, built up from near vortex filaments, is found to be similar to the induced drag the AWES would have in forward flight. The far wake is modeled as two semi-infinite vortex ring cascades with opposite intensity. An approximate solution for the axial induced velocity at the AWES is given as a function of the radial (known) and axial (unknown) position of the vortex rings. An explicit and an implicit closure model are introduced to link the axial position of the vortex rings with the other quantities of the model. The aerodynamic model, using the implicit closure model for the far wake, is validated with the lifting-line free-vortex wake method implemented in QBlade. The model is suitable to be used in time-marching aero-servo-elastic simulations and in design and optimization studies

Raman Micro-Spectroscopy Identifies Carbonaceous Particles Lying on the Surface of Crocidolite, Amosite, and Chrysotile Fibers

Micro-Raman spectroscopy has been applied on UICC (Union for International Cancer Control’s) crocidolite and amosite from South Africa and on UICC chrysotile from Canada. Under Optical Microscope (OM), the surface of the fibers was often characterized by areas, micrometric in size, appearing dark. The laser beam was successively focused on areas of the same sample showing different optical contrasts. On the bright zones, Raman spectra peculiar for crocidolite, amosite or chrysotile were recorded. When dark areas were optically identified, the laser beam was addressed onto these regions and, in the Raman patterns, in addition to the bands produced by the mineral fiber, bands ascribing to substituted carbonaceous phases were observed. These bands were lying in the 4000–1100 cm−1 spectral range. On the basis of the shape of the bands and their relative intensities, suggestions about the order-disorder of the carbonaceous particles could be proposed, and they appeared more ordered on amosite than on crocidolite and chrysotile. From the exposed data, crocidolite and amosite fibers from South Africa, and chrysotile fibers from Canada, largely used in industry in the past, are characterized by many carbonaceous micrometric particles, lying on the fiber surfaces. Based on the noxiousness of the carbon particles on human health, their presence on asbestos fibers may play a role in increasing the carcinogenic effects of the analyzed fibrous minerals

Progettazione di un Data Warehoue per il supporto al controllo qualitativo della produzione di insulina

L’obiettivo di questo lavoro di tesi è quello di realizzare uno strumento a supporto del processo di controllo della qualità per quanto riguarda la produzione di insulina all’interno di un’azienda multinazionale dell’industria farmaceutica. Lo scopo finale è quello di fornire agli utenti dei report uno strumento che certifichi la bontà del farmaco prodotto al fine di decidere la sua immissione sul mercato. Nel particolare l’attenzione di questo lavoro verte sui report che trattano sull’esecuzione dei cicli di pulizia e sterilizzazione che riguardano i macchinari coinvolti nella fase di Formulazione, la fase iniziale del processo produttivo di insulina. Il lavoro svolto prevede un’introduzione sul caso di studio, le attività di progettazione e implementazione del data warehouse, una trattazione sugli strumenti utilizzati, fino ad arrivare al processo di elaborazione dei dati in ingresso e alla rappresentazione grafica delle informazioni agli utenti

Combined preliminary–detailed design of wind turbines

Abstract. This paper is concerned with the holistic optimization of wind turbines. A multi-disciplinary optimization procedure is presented that marries the overall sizing of the machine in terms of rotor diameter and tower height (often termed "preliminary design") with the detailed sizing of its aerodynamic and structural components. The proposed combined preliminary–detailed approach sizes the overall machine while taking into full account the subtle and complicated couplings that arise due to the mutual effects of aerodynamic and structural choices. Since controls play a central role in dictating performance and loads, control laws are also updated accordingly during optimization. As part of the approach, rotor and tower are sized simultaneously, even in this case capturing the mutual effects of one component over the other due to the tip clearance constraint. The procedure, here driven by detailed models of the cost of energy, results in a complete aero-structural design of the machine, including its associated control laws. The proposed methods are tested on the redesign of two wind turbines, a 2.2 MW onshore machine and a large 10 MW offshore one. In both cases, the optimization leads to significant changes with respect to the initial baseline configurations, with noticeable reductions in the cost of energy. The novel procedures are also exercised on the design of low-induction rotors for both considered wind turbines, showing that they are typically not competitive with conventional high-efficiency rotors

Integration of prebend optimization in a holistic wind turbine design tool

This paper considers the problem of identifying the optimal combination of blade prebend, rotor cone angle and nacelle uptilt, within an integrated aero-structural design environment. Prebend is designed to reach maximum rotor area at rated conditions, while cone and uptilt are computed together with all other design variables to minimize the cost of energy. Constraints are added to the problem formulation in order to translate various design requirements. The proposed optimization approach is applied to a conceptual 10 MW offshore wind turbine, highlighting the benefits of an optimal combination of blade curvature, cone and uptilt angles

Free-Form Design of Rotor Blades

This work investigates an integrated free-form approach for the design of rotor blades, where airfoil shapes are treated as unknowns. This leads to the simultaneous optimization of the chord, twist and structural design variables, together with the airfoil shapes along the blade. As airfoils are automatically tailored to the evolution of the blade, this process results in a better exploration of the solution space and relieves the user from the burden of up-front choices, leading to better final designs. The proposed approach is demonstrated by sizing a 2 MW wind turbine blade

From Natural Woods to High Density Materials: An Ecofriendly Approach

Recently, different methods have been proposed to develop wood materials, termed “densified woods”, with density increment and improvement in mechanical proprieties. Almost all the proposed methods involve the use of reducing agents and strong bases. In this work, a new method has been developed involving the use of less polluting agents. The formation of densified woods is divided into two steps: delignification involves the removal of lignin, hemicelluloses, and shorter chains of cellulose, whereas densification involves the plastering of the delignified woods. The obtained materials showed a density increase of two to four times. The obtained densified woods were characterized by spectroscopic, microscopic, and thermogravimetric techniques and mechanical tests. The characterizations aimed at determining the variations of chemical and structural compositions of the samples after delignification and densification processes, showing, respectively, a decrease in lignin and a significant increase in the density and force necessary to bring the materials to yield. The final density of wood was two to three times higher and the force necessary to reach the yield point reached more than three times the initial one for some of the studied samples. These characterizations showed how different woods, with different properties, reach comparable densities and final mechanical properties after delignification and densification process. The increased mechanical properties of the materials allow their application in place of other composite woody materials