1,721,006 research outputs found
Experimental and numerical wind tunnel investigation of the aerodynamics of upwind soft sails
No full textThe present paper reports an experimental/numerical study about the aerodynamics of sails in upwind conditions. This work is part of a wider research frame carried out in the recent years at Politecnico di Milano, involving numerical, wind tunnel and full-scale studies on the aero-hydrodynamics of sailing yachts. The experimental apparatus adopted in this work is the scaled-version of the full-scale setup adopted in the Sailing Yacht Laboratory (SYL) at the same institutions. More specifically, soft sails were tested in wind tunnel in close hauled conditions, properly equipped with thin and soft pressure strips at different sections of head and main sail. Therefore, simultaneous data about distributed pressure, aerodynamic forces and 3D flying shapes were gathered. Fine trimming were investigated during the tests to study the different effect on pressure distribution, performance and sail shapes. The measured sails geometry about the same conditions, fed the steady numerical simulations, based both on Vortex Lattice Method and Reynolds Averaged Navier Stokes equations, for comparison and validation. With regard to the latter, a sensitivity analysis on the simulation parameters was also reported in comparison to experimental results. Aim of this work was to improve the state-of-the-art with an extensive set of combined measurements and computations of different nature and objectives in order to provide a holistic view on the upwind sails aerodynamics
Experimental validation of the aero-servo design of a large-scale floating offshore wind turbine model
No full textOffshore floating wind turbines are such complex systems from the point of view of global dynamics that numerical models are often insufficient in describing completely and correctly their behavior. In this framework large scale models deployed in a natural outdoor environment are a valid complement in understanding the real features of the system and in updating or validating codes. In the case of wind turbines adopting a large scale allows to better reproduce the aerodynamic behavior of the rotor. Objective of the present work is the validation of the aerodynamic design of a large-scale 1:15 model of the DTU 10 MW wind turbine deployed on a multipurpose floating platform, built in the framework of the Horizon 2020 project termed as "The Blue Growth Farm Project". It is requested to assess the effective aerodynamic characteristics of the rotor so to understand if the physical design is well respecting the aerodynamic properties requested in the design phase. Particular care is put in the correct reproduction of the operating parameters as part of the assessment of the control system. For initial analysis a good compliance between design and physical model is found. Regarding the aerodynamic characteristics, a good agreement between the experimental Cp values and the numerical curves is observed. Overall, the physical rotor aerodynamic design is validated and the power controller steady-state performances are assessed
A large-scale wind turbine model installed on a floating structure:experimental validation of the numerical design
Full text linkIn the field of floating wind energy, large-scale wind turbine models deployed in natural environments represent a key link between small-scale laboratory tests and full-scale prototypes. While implying smaller cost, design and installation effort than a full-scale prototype, large-scale models are technologically very similar to prototypes, can be tested in natural sea and wind conditions, and reduce by a consistent amount the dimensional scaling issues arising in small-scale experiments. In this framework the presented work report the aerodynamic and control system assessment of a 1:15 model of the DTU 10 MW wind turbine installed on a multipurpose-platform model for fish farming and energy production. The model has operated for 6 months in a natural laboratory and has been exposed to fully natural and uncontrolled environmental conditions. Assessment is performed in terms of rotor thrust force and power controller parameters such as rotor speed, blade pitch and rotor power as a function of incoming wind speed
Equivalent oscillator approach to model vortex induced vibrations on a circular cylinder
Full text linkThe paper presents a numerical model, based on the equivalent oscillator approach, able to simulate vortex induced vibrations on a circular cylinder. This model consists of a single degree of freedom mechanical system characterized by non-linear parameters that reproduce the fluid-structure interaction in time domain. A genetic algorithm approach was used in order to identify the characteristic parameters of the equivalent oscillator: obtained results are discussed and compared with wind tunnel experimental data and with a previous version of the numerical model. Comparison is performed both in terms of aerodynamic forces and oscillation amplitudes and both in steady and transient conditions
Key parameters influencing wind-induced aeroelastic responses of single-axis solar trackers in photovoltaic plants
Full text linkSingle-axis solar trackers enhance energy production and cost-effectiveness in large-scale solar installations compared to fixed panels. However, their structural design must address unique challenges, particularly regarding wind resistance, due to reduced mechanical properties for cost savings. This article examines several key parameters of solar plants and evaluates their influence on tracker response, emphasizing wind-induced aeroelastic effects. These parameters include the layout arrangement of solar plants and the inter-row spacing. Tracker position has been evaluated in a 4-rows by 2-column corner region of rectangular tracker plant, with two ground cover ratios of 0.38 and 0.25. Moreover, the effects of the operational parameters of individual trackers have also been monitored, considering working pitch angles in the range between −60∘ and +60∘ and wind exposure angles of 0°, 15°, 30° and 45°. Structural properties were assumed to remain constant. The research combines experimental wind tunnel tests with numerical dynamic simulations based on a finite element model, monitoring the internal stress state to assess performance. Results show that large pitch angles (>45∘) exhibit stable aeroelastic behavior, while small pitch angles, between −30∘ and +30∘, become unstable after reaching a certain velocity threshold. Among the monitored pitches, inclinations between 15° and 30° are the most critical in terms of internal response. The research confirms that trackers on the perimeter are the most stressed in the plants. The largest load cases occur with wind directions normal to the tracker axis. Finally, the analysis of the spacing between rows showed no significant effect on the response
A Techno-Economic Analysis of a Cargo Ship Using Flettner Rotors
Full text linkIn the last twenty years, the global shipping transport demand has strongly increased (around 4% per year since the 1990s), together with the request for new green propulsion technologies to break down carbon emissions and face the costs deriving from the usage of conventional diesel fuels. Flettner rotors (hereafter: FRs) have been identified by several researchers as a promising solution to exploit wind energy on commercial ships, reducing fuel consumption. The present work presents a six-degree-of-freedom (6DOF) ship performance model set up to evaluate the best way of using a pair of Flettner rotors. The study analyses the performance of this propulsion system in consideration of weather and sea conditions, evaluating the related reduction in fuel consumption. A discussion about the economic and environmental advantages of the usage of FRs is provided, considering the costs linked to their installation and the new emission restrictions. Relevant results have been obtained for different routes, speed ranges and rotor dimensions while investigating the best Flettner rotor arrangement to minimise both the emissions and the installation cost payback period
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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