109 research outputs found
Aeroelasticity of Membrane Kites: Airborne Wind Energy Applications
No full textThe climate actions defined by United Nations require a rapid transition to low environmental footprint technologies. The energy sector is the major emitter of carbon dioxide emissions and a significant contributor to extracting resources for fuel and power plant construction materials.Wind energy is projected to produce a significant share of electricity and energy in the following decades. The wind turbines have a small footprint during the operation, but the turbine with its foundation is a massive structure with a significant material footprint. Airborne wind energy uses tethered devices to harness high-altitude wind energy, substantially reducing bulk material use. However, better models are required to make the systems reliable and efficient. This thesis focuses on membrane traction kites that harness wind energy by flying fast crosswind maneuvers. A high-fidelity aeroelastic model for the kites is developed to predict the aerodynamic loads and the structural deformations of real systems. The aeroelastic model assumes that the membrane kite flight can be modeled as multiple steady-states without memory from the past. The steady-state aerodynamics are simulated by solving the incompressible Reynolds-averaged Navier-Stokes equations numerically. High-quality numerical grid generation strategies are developed for the unconventional wing shape of the membrane kites. The membrane kites are tensile structures, and therefore a finite element model with cable and membrane elements without rotational degrees of freedom is used to calculate the deformed shape. The solver calculates the average surface without wrinkles and applies an additional model when an element is under compression. The steady-state response of the structure is calculated with a dynamic relaxation technique. The two solvers are coupled in a partitioned manner, and during each iteration, both solvers compute a steady state. The staggered approach requires several coupling iterations to converge. The fluid mesh needs to be altered to the deformed geometry during each iteration, and therefore, the mesh is deformed with radial basis function with greedy point selection.This thesis presents three computational studies with the framework. The first two studies focus on the aerodynamics of rigidized LEI kite airfoil and wing. The aerodynamic model is validated with an already existing wind tunnel experiment on a similar airfoil. Generally, the largest model uncertainty in CFD is the mesh and therefore, the uncertainty is assessed by mesh refinement studies. A range of flight conditions is simulated by varying the inflow angle of attack, sideslip angle and Reynolds number. The flow around the wing is characterized by a recirculation zone behind the leading edge tube due to the lack of second skin. The zone is highly influenced by the inflow conditions. The effect of the chordwise inflatable tubes on aerodynamics is assessed by creating a model with and without them. The results show that the chordwise tubes have an almost negligible impact on the aerodynamic forces, which suggests they could be left out of the aerodynamic model in future work, simplifying the mesh generation and mesh deformation.The third study shows the aeroelasticity of a ram-air kite for several power configurations by changing the trim of the bridle lines. The kite forms a typical ram-air shape with ballooning in between ribs, and the nose of the wing is flattened at the stagnation region. The aerodynamics of the flexible kite is compared to a rigidized version of it. The wing is fixed at the symmetry plane and fixed to the pre-inflated shape with stagnation pressure. The results show that the flexible kite is aerodynamically more efficient than the rigidized version. The morphing wing adapts itself to the incoming flow in a way that extends the range of feasible flight conditions and improves efficiency. The aeroelastic framework converges satisfactorily with all the power setups, and it is computationally relatively inexpensive for fidelity. Consequently, the framework could be integrated into a membrane kite design process and could be a valuable asset in evaluating kite designs.Wind Energ
Verslag behorende bij het processchema: Bereiding van isopropyl-alkohol
No full textDocument(en) uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Ammoniakproductie volgens ICI patent EP 0 212 889
No full textDocument(en) uit de collectie Chemische ProcestechnologieDelftChemtechApplied Science
Biomonitoring and assessment of atmospheric trace elements in Portugal: Methods, response modelling and nuclear analytical techniques
No full textApplied Science
Effectieve informatie-uitwisseling binnen Nederlandse DBFM weginfrastructuurprojecten
No full textSince ten years contractors receive another question of public clients (government, local authorities) in the Dutch Civil Engineering sector. This question is in the form of integrated contracts, in which design, construction and/or maintenance are clustered. In projects contracted with the contract form Design (D), Built (B), Finance (F) and Maintain (M) the contractor is responsible for the design, construction and maintenance of the asset in question. This market approach results to freedom and responsibility for contractors. Firstly, a contractor has the freedom to make LCB considerations. Secondly, contractors become responsible for the delivery of performance during construction and maintenance. Currently, several Dutch DBFM infrastructure projects are in the pipeline. The government intends to spend the upcoming years more money on projects with the contract form DBFM. The construction has high failure costs with costs are 8-10% of the total contract value (SBR, 2013). A study by USP Marketing (2011) indicates that the failure costs consist in 21% by limited exchange of information. The information exchange is with 2% of the total contract value the biggest factor for failure costs. There is a freedom to make LCB considerations and responsibility for the provision of services for new contractors. This includes the exchange of information in order to make and give meaning to the agreed performance. How do contractors organize the exchange of information with freedom they get for LCB considerations and responsibility for delivering performance? The core issue in this research is that contractors make limited use of information for LCB considerations from various information carriers in practice which determine the life cycle costs. This information is available within the organization, but information on system characteristics and behavior are insufficient exchanged between the design team and the carriers during the design phase. The purpose of this study is to determine whether effective exchanges of information takes place when making design choices and to do recommendations for effective information exchange. The conclusion is that there is insufficient effective exchange of information (1) within Dutch DBFM infrastructure projects. Therefore there is enough untapped potential (2) for a more effective exchange of information. Contractors in Dutch DBFM infrastructure projects do not work according to Systems Engineering (SE) as ideally prescribed by literature. SE is an approach in which information is created by through processes. Following the SE standard leads to Structures in which information can be recorded, stored, shared and recalled Information is structured data that can be recorded on a computer. (Examples are) such as functions, risks, requirements and objects. To determine whether this information exchange is effective, there are conditions established where information must meet. In this study the conditions are based on the problems of LCC analyses. This study defines effective information exchange when information is relevant (1a), available (1b), punctual (2), explicit (3) and traceable (4). To test the conditions for effective exchange of information in practice, the conditions are processed into questions. These questions are part of interviews. Another part of the interviews are the DBFM contract requirements. Within a DBFM contract the requirements should be central to several teams of a contractor. For the interviews are relationships between Requirements and Functions (a), Requirements and Organizations (b), Requirements and Locations (c), Requirements and Stages (d), Requirements and Objects (e) and Requirements and Risks (f) tested. The results show the candidates find information relevant, but the information is not always available. In addition the information available is not on time, not explicitly or not traceable. The differences between theory and practice in information exchange have been identified for five of the six tested relationships. Only the relationships between the Requirements and Organizations (b) are in accordance with the criteria that more than 50% of the respondents are satisfied with all conditions. This relation satisfies the conditions for effective exchange of information, but is debatable. This is debatable, since this relation is the only satisfied relationships between requirements and other Structures. Therefore there is missing information for context and coherence. Contractors think that by allocating requirements on parts of the organization is sufficient for working with SE. Contractors experience SE in practice as a form of managing the requirements, imposed by public clients. In addition, in practice, the focus is located on the requirements of the design and the construction and not in the maintenance. This does not in accordance for LCB considerations. The main recommendation is to send in information exchange, whereby one central information management system (ON-1) is needed that addresses the processes of employees in the project. A second recommendation is a change of working and vision of contractors. SE is contractually obliged for contractors by a client. A contractor should see SE more as a chance. SE can be used as a tool for information exchange. A contractor should do SE as an opportunity. To take this opportunity the different recommendations need to be done for effective exchange of information: execute the processes (ON-2), interpret the ISO15288 together (ON-3) and capture the generated information in Structures (ON-4). Then information can become more timely, explicit and traceable. With these changes effective information exchange can take place and contractors can make LCB considerations according to the agreed performance. Upholding the freedom and responsibility can lead to a reduction in failure costs through more effective information exchange.Construction Management and EngineeringStructural EngineeringCivil Engineering and Geoscience
Marktrisico in projectontwikkeling
No full textThe financial crisis and economic recession revealed the vulnerability of the real estate development branch as a result of volatility on the markets. The complex process of real estate development requires understanding of both the markets to be traded on and segments within these markets. The research investigates how a real estate development company is able to apply a diversification strategy in the development portfolio. The reduction in market risk as a result of portfolio diversification is calculated using the market risks of office, retail and residential developments, based on long term time series of the construction market, the space market and investment market. Market risk may be decreased by 18% - 20% by developing retail and residential space. Operational risks tend to increase when mixing multiple segments within a building or within a company.Design and Construction Management, Building EconomicsReal Estate and HousingArchitectur
Synergistic Effect of a Flavonoid-Rich Cocoa–Carob Blend and Metformin in Preserving Pancreatic Beta Cells in Zucker Diabetic Fatty Rats
No full textAuthor Contributions: Conceptualization, T.F.-M., L.V., M.A.M. and E.F.-M.; Data curation, P.G.-V., M.A.M., E.F.-M., T.F.-M., L.V., A.M.V. and S.R.; Formal Analysis, P.G.-V., M.A.M., E.F.-M., T.F.- M., L.V., A.M.V. and S.R.; Funding Acquisition, M.A.M., E.F.-M., T.F.-M., L.V., A.M.V. and S.R.; Methodology, P.G.-V., T.F.-M., L.V. and E.F.-M.; Project administration, M.A.M., T.F.-M., L.V. and S.R.: Writing—Original Draft P.G.-V., M.A.M. and E.F.-M.; Writing—Review and Editing P.G.-V., M.A.M., E.F.-M., T.F.-M., L.V., A.M.V. and S.R.; All authors have read and agreed to the published version of the manuscript.The loss of functional beta-cell mass in diabetes is directly linked to the development of diabetic complications. Although dietary flavonoids have demonstrated antidiabetic properties, their potential effects on pancreatic beta-cell preservation and their synergistic benefits with antidiabetic drugs remain underexplored. We have developed a potential functional food enriched in flavonoids by combining cocoa powder and carob flour (CCB), which has shown antidiabetic effects. Here, we investigated the ability of the CCB, alone or in combination with metformin, to preserve pancreatic beta cells in an established diabetic context and their potential synergistic effect. Zucker diabetic fatty rats (ZDF) were fed a CCB-rich diet or a control diet, with or without metformin, for 12 weeks. Markers of pancreatic oxidative stress and inflammation, as well as relative beta-cell mass and beta-cell apoptosis, were analyzed. Results demonstrated that CCB feeding counteracted pancreatic oxidative stress by enhancing the antioxidant defense and reducing reactive oxygen species. Moreover, the CCB suppressed islet inflammation by preventing macrophage infiltration into islets and overproduction of pro-inflammatory cytokines, along with the inactivation of nuclear factor kappa B (NFκB). As a result, the CCB supplementation prevented beta-cell apoptosis and the loss of beta cells in ZDF diabetic animals. The observed additive effect when combining the CCB with metformin underscores its potential as an adjuvant therapy to delay the progression of type 2 diabetes.Ministerio de Ciencia, Innovación y UniversidadesComunidad de MadridSección Deptal. de Bioquímica y Biología Molecular (Farmacia)Fac. de FarmaciaTRUEpu
Een tweedimensionale getijberekening ter bepaling van de gevolgen van de aanleg van een zanddam in de Noordzee t.b.v. de aanlanding van LNG en LPG
No full textIn juni 1977 heeft de NV. Nederlandse Gasunie na vijf jaar onderhandelen een contract afgesloten voor de levering van vloeibaar aardgas (LNG) door de Algerijnse staatsmaatschappij Sonatrach. Dit contract is in combinatie met de Duitse firmás Ruhrgas AG en Salzgitter Ferngas GmbH gesloten. Te beginnen omstreeks 1984 zal gedurende twintig jaar twaalf miljard kubieke meter gas per jaar worden geleverd, waarvan zes miljard kubieke meter aardgas voor Nederlands gebruik. Het vloeibare aardgas zal met tankers worden aangevoerd naar een Nederlandse haven, alwaar het gasvormig wordt gemaakt en vanwaar het via het bestaande distributienet naar de consument wordt gevoerd. De resultaten van dit onderzoek zijn goed bruikbaar voor nader onderzoek naar de zanddam. Er mag geconcludeerd worden dat het getij-onderzoek een positieve waarde heeft.Hydraulic EngineeringCivil Engineering and Geoscience
Impact of Turning Induced Shape Deformations on Aerodynamic Performance of Leading Edge Inflatable Kites: Master Thesis
No full textWith growing energy demands and a need to switch to a sustainable source of energy key stakeholders are considering the use of high altitude wind energy systems. TU Delft and its start up company kitepower are key stakeholders investigating the commercial viability of this technology. With this goal the research group has developed several kite systems capable of accessing high altitude winds. It is believed that the low investment cost and high performance of kites could lead to a lower cost of energy. Concepts currently being considered involve a leading edge inflatable (LEI) kite that is controlled by an on-board control unit and is connected to a ground-based generator. Once the kite is deployed to the required altitude it enters a power generation stage where it is flown in a figure eight routine. This routine is controlled by the on-board control unit that pulls on tethers that are connected to the tip of the kite. This process is followed by a retraction phase where the kite is pulled back in. The goal of the system is to maximize energy production in the generation phase while limiting the energy consumed in the retraction phase. It is critical to assess and improve the kite design and its performance at all stages of operation such that the net power production can be maximized. While significant advancements have been made into the performance for normal flight there is a lack of research on the aerodynamic performance when there is control input to initiate a turn. The shape of the kite and the high angle of attack at which the kite is flown results in complex flow behavior involving separation, flow vortices, flow reattachment etc. This poses several challenges to maintain accuracy. A computational approach involving a steady-state Reynolds-averaged Navier Stoke (RANS) simulation is believed to be a computationally viable mode of analysis to capture the flow behavior. This thesis details the approach used to improve results attained using this method and understand the influence of deformations associated with control inputs on the aerodynamic performance of the kite. A control input is simulated using a finite element model (FEM) with the Abaqus software by reducing the length of the right steering and increasing the length of the left steering line by 0.5 m. This results in the right side reducing its curvature and being pulled towards the kite control unit (KCU). Whilst on the left side the bridle lines are less tensed, leading to an increase in curvature. The turning performance is governed by the offset and variations in magnitudes of forces. Meshes are generated that attempts to minimize geometry alterations whilst still maintaining high quality. The influence of boundary layer parameters are investigated. A trade-off is made where the influence of key parameters on accuracy and computational time is evaluated; where applicable improvements are made. Both the global as well as the local parameters of the kite in normal as well as turning orientation are analyzed. The results show that control induced deformations lead to a percentage reduction in the lift, whilst the effect on the drag is minimal. It is further seen that the kite initiates stall at an angle of approximately 40 degrees. The stall behavior is initiated at the mid-span of the kite and gradually moves to the tip. The turning performance is measured by looking at the yaw moment. The magnitude of this parameter is linked to the offset and magnitude in force vectors at the tip. Due to the delayed stall at the tips, it is observed that the yaw moment increases beyond 40 degrees. Accuracy issues using this method were seen when performing a validation study on a profile similar to that of the kite. These issues could be due to limitations of the method or potential errors in the reference study. It is recommended to reevaluate the validation study before using this method for detailed flow analysis. It is concluded, that in order to fully trust the relevance of the results, one would have to have to conduct a validation study. However the method’s ability to address non-linear flow effects within a limited time frame makes it a viable option for design optimization/system modelling.Aerospace Engineerin
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