112 research outputs found
1.3 μm passively Q-Switched bismuth doped fiber laser using Nb<sub>2</sub>C saturable absorber
No full textA tunable passively Q-switched fiber laser operating at 1.3 μm was demonstrated using bismuth-doped fiber (BDF) as the gain medium and using niobium carbide (Nb2C) as the saturable absorber (SA). The Nb2C was prepared using the solution casting method, and then fabricated into a film form for ease of integration into the laser cavity. Stable Q-switched pulses were observed as the pump power was increased from 820 to 1037 mW, generating pulses with increasing repetition rates from 10.1 kHz to 13.8 kHz and decreasing pulse widths from 17.54 to 7.58 μs. The all-fiber laser had a center wavelength at 1314 nm with a broad 3-dB bandwidth of 8.35 nm. The maximum output power and pulse energy of the Q-switched laser were 0.74 mW and 53.7 nJ, respectively. The laser was stable when tested for its long-term stability, where the peak frequency remained consistent at 13.8 kHz and the SNRs were maintained to be more than 60 dB throughout the entire test period. To the best of our knowledge, this is the first demonstration for a passively Q-switched fiber laser operating at 1.3 μm wavelength region using BDF as the gain medium
System-level assessment of tail-mounted propellers for regional aircraft
No full textThree regional transport aircraft of different configuration are synthesized for the same design specification using an automated design routine. The first aircraft features wing-mounted propellers, the second aircraft features propellers mounted on the horizontal tail plane, while the last configuration replaces the horizontal and vertical tail with two ducted propellers mounted near the rear of the fuselage. These last two innovative configurations have the potential to reduce the cabin noise, while the ducted propeller could also reduce community noise. The analysis and design methods to size and analyze these configurations include weight and balance, stability and control, aerodynamic performance, and mission performance. Propeller slipstream effects are taken into account and demonstrated to play an important role in the sizing of the horizontal tail surface. A comparison study between the three aircraft for a harmonic mission of 1530km and 7500kg payload demonstrates that the aircraft with wing-mounted propellers has the lowest maximum take-off mass and burns the least amount of fuel. The two innovative configurations have slightly less performance, which is ultimately attributed to the large center-of-gravity excursion that stems from an aft-mounted propulsion system. A 3% increase in maximum takeoff weight is predicted along with a fuel burn increase between 5% and 10% for the innovative configurations, respectively. Further investigation of the underlying assumptions might improve these results in future studies.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and Propulsio
Supporting MDO through dynamic workflow (re)generation
No full textThe use of advancements in computing technology has enabled designers to perform more thorough and more detailed design studies. Multidisciplinary Design Optimization (MDO) architectures provide users with guidelines on how to structure their MDO problem, including the linking of disciplines and how to perform the optimization. However, complex MDO problems can consist of tens of disciplines and hundreds of design variables. Thus, the set-up of these problems can be complex and time consuming. In an attempt to reduce the time required and complexity of this set up, the main goal in this thesis is: "To develop and demonstrate a methodology for automatic workflow (re)generation to support MDO". The method to fulfill these requirements consists of three main steps. The first is the automatic generation of microworkflows, workflows representing the different disciplines of the problem. The user will need to specify the inputs, outputs and operations, after which the workflows are automatically generated. The second step involves the automatic storage of workflows. Workflows are stored in a graph database, allowing the addition of semantics to the data. Adding semantics allows a reasoner to understand what the data means, enabling the inferring of data not explicitly defined. OWL (Web Ontology Language) ontologies are used to supply structure to the workflow data and add semantics. In addition, materialization scripts are present to regenerate stored workflows. The final step of the implementation involves the automatic generation of simulation workflows according to different MDO architectures. This generation involves the materialization and adjustment of microworkflows and the creation of a ‘higher level’ workflow that links the disciplines and performs the optimization. The implementation of the automatic architecture generation has been validated using three case studies of varying complexity, amount of disciplines and discipline couplings. These case studies have shown a reduction of 93 to 98 % of time spent on the generation of simulation workflows representing the problem using an MDO architecture. In addition, the approach reduces the required user expertise and minimizes the amount of information the user needs to provide.Aerospace EngineeringFlight Performance and Propulsio
Sediment exchange between the main channel and the groyne fields of a river
No full textReport on a physical scale model test in the Fluid Mechanics lab on the effect of groynes on the bed and sediment transport in rivers.Hydraulic EngineeringCivil Engineering and Geoscience
The effect of groynes on rivers: Literature review
No full textGroynes are structures constructed at an angle to the flow in order to deflect the flowing water away from critical zones. They are made of stone, gravel, rock, earth, or piles, beginning at the riverbank with a root and ending at the regulation line with a head. They serve to maintain a desirable channel for the purpose of flood control, improved navigation and erosion control. In the River Rhine, which is considered the backbone of North-western European waterways network, the primary objective of groynes is to provide a fairway of sufficient depth and width. For example the River Waal, the most important branch of the Rhine River in the Netherlands is regulated by around 500 groyne. Within the framework of the research project "Space for the Rhine Branches" several measures have been devised to achieve a decrease of the water levels at peak discharges, one of those measures, is lowering of the existing groynes. The rationale behind this proposal is that; due to large-scale erosion of the low-water bed through the past decades, the groynes are now higher than necessary for keeping the main channel at depth. Lowering the groynes along certain reaches of the river would result in a reduction of the effective roughness during high water conditions thus, increasing the river's flood conveyance capacity. If the groynes are lowered, however, the balance of hydrodynamic forces acting on the groyne-fields will change, and there will be a large-scale morphological impact. To identify this impact, a thorough understanding to the effect o f groynes on the morphology of the river is necessary. The sediment exchange between the groyne-fields and the main channel needs to be more comprehensible. The purpose of this report is to acquire the background knowledge required to study the effect of groynes on a river. The characteristics of the existing groyne-fields along the Waal River are presented. The hydrodynamic and morphological impact of groynes on a river is described. Moreover, because navigation plays an important role in the interaction between the groyne fields and the main channel, the navigation induced water motion and its effect on the flow in groyne-fields is described. Finally, a review of some prediction attempts to the interaction between the groyne-fields and the main channel is presented.Hydraulic EngineeringCivil Engineering and Geoscience
Un ampliamento della biblioteca di Giovanni Della Casa
No full textThis paper proposes a different reading of the inventory of Giovanni Della Casa’s library to the one carried out previously by Lorenzo Campana and Emanuela Scarpa. Starting from a general description of the document, included in the manuscript volume Vat. lat. 14826, the author assigns to Giovanni Della Casa titles which Campana and Scarpa had attributed to Ubaldino Baldinelli (whose library, or part of it, was included in Della Casa’s in 1551). The author also attempts to identify some of these editions and proposes to date the inventory to 1551, when Della Casa was about to take definitive leave of Rome to move to Venice
Drag reduction through a streamlined aerodynamic design process: Development and implementation of a methodology to accelerate the aerodynamic design process in the preliminary phase of car design
No full textContinuous innovation is very important to stay competitive in today’s world. Automotive manufacturers are an excellent example of this evolution when looking to new vehicle concepts. But also behind the scene, they have to be innovative in order to be able to keep up this progression. Aerodynamics has a large influence on the total performance of the car, and therefore fulfils a very important role in this innovation story. Aerodynamics is absolutely not straightforward which makes it on the one hand difficult to deal with and to estimate it influences, but on the other hand, this creates an improvement potential. Today’s passenger cars are already aerodynamically optimised to a fairly large extent, meaning improvements become rather marginal. To be able to keep this tendency of improving in the future, the aerodynamic design process has to be adapted. The focus of this work will be on the reduction of the air resistance of cars, which has a large influence on its top speed and fuel consumption. Especially the latter is very important today and will even gain more importance for future cars. Earlier research has shown that 70% of the reduction of the air resistance and the corresponding Cx value is done during the preliminary aerodynamic design phase. This phase is characterised by a high design freedom and a low level of detail of the corresponding design. Due to this, this early phase invites for shape optimisation of the basic aerodynamic shape having much more potential to achieve a lower Cx value. At the end of this phase, all fundamental parameters, dimensions etc. that define the final car will be fixed in order to begin the further detailed design during which detail optimisation is only possible anymore. This fundamental difference between the early phase and subsequent detailed design is responsible for their difference in influence on the final achieved Cx value and reduction. In order to achieve a successful aerodynamic design in terms of air resistance, the importance of that early design phase cannot be underestimated. To prevent aerodynamic improvements from stagnating, this preliminary design phase has to be fully exploited. Those preliminary phase can be split into three specific sub phases, namely the initial phase, preliminary studies and concept phase. In the first, the high level targets of the car design will be determined, which the final design should comply with. After this, as much as possible information and knowledge about the design has to be gathered during the so called preliminary studies. This knowledge will be used to formulate thoughtful concepts for the subsequent concept phase where they will be assessed and developed further until one final design concept remains which should comply with all the earlier defined high level targets. The quality of the information and knowledge gathered during those preliminary studies is therefore critical for a comprehensive final design. This is valid for the whole aerodynamic design and by extension also the total car design. But as already said, this work focuses on the design of the car exterior in terms of Cx value. It was observed in this work that the current situation has potential for improvement. More specifically, it was noticed that the aerodynamic department is occupied mainly with detail optimisation instead of the more favourable shape optimisation during those preliminary studies. The reason for this is due to a combination of their minor influence on the car exterior design compared to the aesthetics department and the current process flow during those studies. This current process flow is very inefficient and contains too much time-consuming and repetitive manual work. This combined with the short timespan of those preliminary studies lead to a limitation of the gathered knowledge of the car exterior design that is investigated. This is the main reason why the aerodynamicists are currently doing mainly detail instead of shape optimisation. For the latter, more investigations of higher quality (higher order) are required, which the current inefficient process flow does not allow for. Therefore, the aerodynamicists are limited to detail optimisation because of this, which is explained more into detail in this work. Thus, adapting the current process flow to allow the aerodynamic department to do shape instead of detail optimisation was found to be the main solution to improve and further reduce the Cx value and prevent it from stagnating in the future. The current process flow of those preliminary studies was analysed in this work and a suggested methodology that could accomplish those improvements was formulated based on this. The main difference of this methodology compared to the current situation is the implemented closed-loop instead of the open-loop modelling of the aerodynamic behaviour during those preliminary studies. This requires a fully automated process flow, which is missing in the current situation. In order to be able to also work out this suggested methodology to a fully working process flow, an automated generation of the geometric variants have to provided. This was achieved by developing a parametric geometry model capable of instantly delivering the required geometric variant without human interaction. The parametric model is an approximation of the real car exterior geometry, but its accuracy was proved with relevant CFD simulations. The closed-loop surrogate modelling is realised by using a MATLAB-based toolbox, called SuMo-toolbox, which is implemented in the software framework of the developed methodology. A secure shell connection between this software framework in MATLAB and the Linux machine, on which the simulations are done, assures a stable and fully automated process flow. After this working out of the presented methodology, a reality-based use-case was done to estimate its potential for improvements compared to the current situation. Promising results were already obtained which also confirm the promised theoretical improvements in praxis. Also conclusions and recommendations for future work or alternative implementations and extensions of this methodology are formulated in this work. This work was meant as an initial step and incentive to apply this methodology in the current industry. Before this could be possible, further research and work has to be done to make it practically implementable. This new process flow means a drastic change of the current one. It is typical for large companies to be unwilling to take this step. But if this methodology could be further developed so that it could fulfil its supposed role, namely improving and further reducing the Cx value of cars, it will become an important tool in the (near) future for manufacturers to become or stay ahead of their competitors. Certainly in today’s world of increasingly strict economics, its role cannot be underestimated.Flight Performance & PropulsionAerospace Engineerin
Una lettera perduta di Giovanni Della Casa a Piero Vettori e la corrispondenza burlesca con Antonio Bernardi della Mirandola
No full textThe essay informs of the discovery of a lost letter by Giovanni Della Casa to Piero Vettori in the Livorno Library F. D. Guerrazzi : the missive was published in the Eighteenth-century edition of Della Casa’s Opere and the author provides a new transcription in the Appendix. The essay compares the missive with two other
contemporary letters, focusing on the controversy that arose in those months around the diffusion of the Commentarius by Antonio Bernardi della Mirandola, a philosopher protected by Cardinal Alessandro Farnese. The author eventually claims that also the comic tenzone between Della Casa and Antonio Bernardi should be connected to this controversy, which involved many Florentine friends close to Della Casa (in particular Ubaldino Bandinelli). Through the literary skirmish, Della Casa wanted to mitigate the controversy with Bernardi, with whom he maintained, in the following years, a relationship of friendship and convenience
Produktie van vloeibare brandstoffen uit aardgas
No full textDocument(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science
Scalability analysis of radical technologies to various aircraft class: Part 1: initial designs
No full textVarious research initiatives in hybrid-electric/sustainable aviation typically address only a single vehicle or single vehicle class. However, novel propulsion and energy solutions can be expected to be differently applied in different vehicle classes. The objective of the EU funded research project CHYLA (Credible HYbrid eLectric Aircraft) is to identify areas suitable for scaling, as well as limitations or challenges for development for the applications of key radical technologies on different classes of aircraft. This article provides an overview of the design approach followed for the CHYLA project, as well as initial radical designs and comparison to the CHYLA baselines. These provide the starting point for both the sensitivity study which will be presented in a later scalability assessment and economical assessments in the CHYLA project. A variety of regional, short medium range and large aircraft has been designed, all according to the same TLAR yet without detailed tuning of important power control variables. Results are distinguishable between concepts and provide sufficient detail to capture the necessary effects. The reduction of fuel consumption will require detailed assessment and fine tuning, though reductions may be achievable for regional and possibly SMR aircraft
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