Comportement aérodynamique d'une éolienne offshore flottante soumise à un effet de houle

International audienceThe flowfield around the rotor blades of a wind turbine may be quite complex due to the occurrence of several aerodynamic phenomena. It is all the more true for floating offshore wind turbines (FOWT), for which the six rigid-body motions of the floating platform can induce blade/wake interactions. Therefore conventional numerical approaches for wind turbine applications, such as BEM, may be questionable for an accurate prediction of floating wind turbine aerodynamic loads. Consequently, the current paper investigates the aerodynamic behavior of a FOWT subjected to several prescribed motions, representative of a wave movement, based on CFD simulations. These results, obtained on the NREL 5-MW wind turbine, are compared to previous results found in the literature and analyzed to provide a better understanding of the involved aerodynamic phenomena

CFD Modelling and Simulation of Water Turbines

The design and development of water turbines requires accurate methods for performance prediction. Numerical methods and modelling are becoming increasingly important tools to achieve better designs and more efficient turbines, reducing the time required in physical model testing. This book is focused on applying numerical simulations and models for water turbines to predict tool their performance. In this Special Issue, the different contributions of this book are classified into three state-of-the-art Topics: discussing the modelling of pump-turbines, the simulation of horizontal and vertical axis turbines for hydrokinetic applications and the modelling of hydropower plants. All the contributions to this book demonstrate the importance of the modelling and simulation of water turbines for hydropower energy. This new generation of models and simulations will play a major role in the global energy transition and energy crisis, and, of course, in the mitigation of climate change

Numerical investigation of a free standing horizontal axis tidal turbine

The thesis describes a set of studies carried out in parallel with a tidal turbine design program which was undertaken by the Turbomachinery Group to which the author belonged to during the duration of this project. Therefore the work presented in this thesis constitutes an exploration of the physics of horizontal axis tidal turbines and of the modelling issues associated with the simulation of these devices. Specifically the investigation centered on the behaviour of the turbine when exposed to the influence of tidal channel waves. The numerical analysis of the free standing, gravity stabilised horizontal axis tidal turbine (HATT) was carried out with the application of Speziale’s Reynolds Stress Model (hereafter know as Speziale, Sarkar and Gatski or SSG model) available in the CFX CFD code. The use of a number of turbulence models was investigated but poor convergence or starting difficulties led to the employment of the SSG Reynolds Stress turbulence model. Simulations for a range of test cases were undertaken ranging from single blade passage cases to transient simulations which included the motion of the turbine and the variation of the flow velocity due to the combined action of waves and the shearing effects of the sea bed boundary layer. A number of CFD results were compared to experimental data acquired from tests conducted on a scale model in the summer of 2009 at the IFREMER test flume in France. An additional source of comparison is provided by data obtained from a BEMT code produced by the CU consultant, Mr Chris Freeman, (Freeman et al., 2009a). A number of numerical models were assembled to analyse the effects of the presence of the pylon and blade-pylon spacing. These were run as steady and unsteady cases. For the steady cases several angular positions were examined to investigate the effects of the transit of the blades through the pylon potential field and across the sea bed boundary layer shear flow. An idealised no-pylon case was analysed to compare with the equivalent model with pylon. On average there was a performance increase of 2% for this configuration when compared to the case with pylon for the datum spacing. The simulations covered four turbine rotational speed cases. These correspond to a startup condition and to rated power, with an intermediate point, and to an overspeed regime. In the overspeed condition the power is essentially unchanged but the thrust reduction is strong. Additional investigations covered the performance of the turbine when yawed and the influence of inflow turbulence. The comparisons between the solutions obtained from steady-state and transient simulations showed that the unsteady approach is preferable to describe these types of flow. Two waves were employed in conjunction with the transient models. The first corresponded to a moderate sea state (1:5m height and 10:0s time period) of the type occurring more frequently. The second case involved a substantial wave (3:0m height and 14:0s time period) which is associated with storm conditions. The datum models which incorporated the most energetic wave showed similar values for the torque observed on the transient simulations without waves for the overspeed and rated power cases respectively. This is a significant finding given that the 15m diameter turbine is immersed in a 35m tidal channel. The peak value for the axial thrust and torque on the large wave simulation is on average 86% and 90% higher than the steady state thrust and torque respectively for the rated power case. The loads imposed on the rotor system for the large wave are approximately 3% higher than those of the regular wave. Similar detailed studies for tidal turbines are non-existent at time of publication. The work is therefore unique in the scope and breath of the simulations it contains. The computational resources required were vast. Transient simulations including wave effects took three weeks of computation time utilizing sixteen processors. Each of these cases required about several terabytes of storage space to record the intermediate transient results

Numerical Simulation of Wind Turbines

The book contains the research contributions belonging to the Special Issue "Numerical Simulation of Wind Turbines", published in 2020-2021. They consist of 15 original research papers and 1 editorial. Different topics are discussed, from innovative design solutions for large and small wind turbine to control, from advanced simulation techniques to noise prediction. The variety of methods used in the research contributions testifies the need for a holistic approach to the design and simulation of modern wind turbines and will be able to stimulate the interest of the wind energy community

A cumulative index to a continuing bibliography on aeronautical engineering

This bibliography is a cumulative index to the abstracts contained in NASA-SP-7037(184) through NASA-SP-7037(195) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract, report number, and accession number indexes

Multidisciplinary Design Optimization of an Aircraft Considering Path-Dependent Performance

Aircraft are multidisciplinary systems that are challenging to design due to interactions between the subsystems. The relevant disciplines, such as aerodynamic, thermal, and propulsion systems, must be considered simultaneously using a path-dependent formulation to accurately assess aircraft performance. The overarching contribution of this work is the construction and exploration of a coupled aero-thermal-propulsive-mission multidisciplinary model to optimize supersonic aircraft considering their path-dependent performance. First, the mission, thermal, and propulsion disciplines are examined in detail. The aerostructural design and mission of a morphing-wing aircraft is optimized before the optimal flight profile for a supersonic strike mission is investigated. Then a fuel thermal management system, commonly used to dissipate excess thermal energy from supersonic aircraft, is constructed and presented. Engine design is then investigated through two main applications: multipoint optimization of a variable-cycle engine and coupled thermal-engine optimization considering a bypass duct heat exchanger. This culminates into a fully-coupled path-dependent mission optimization problem considering the aerodynamic, propulsion, and thermal systems. This large-scale optimization problem captures non-intuitive design trades that single disciplinary models and path-independent methods cannot resolve. Although the focal application is a supersonic aircraft, the methods presented here are applicable to any air or space vehicle and other path-dependent problems. This level of highly-coupled design optimization considering these disciplines has not been performed before. The framework, modeling, and results from this dissertation will be useful for designers of commercial and military aircraft. Specifically, optimizing the design and trajectory of commercial aircraft to minimize fuel usage leads to a more sustainable and more connected world as the rate of air travel continues to increase. The methods presented are flexible and powerful enough to design supersonic military aircraft systems, as demonstrated using an application aircraft. This dissertation has been shaped through direct collaborations with NASA, the Air Force Research Lab (AFRL), and other academic institutions, which shows the broad appeal and applicability of this work to a multitude of design problems.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/155269/1/johnjasa_1.pd