Key words. Turbine design, **Blade** **Element** **Momentum** theory, Computational Fluid Dynamics, Geometry Modeling, Wind Turbine Aerodynamics, Fluid–Structure Interaction
AMS subject classifications. 76G25, 76M99, 65Z05
1. Introduction. The **Blade** **Element** **Momentum** (BEM) theory is a model used to evaluate the performance of a propelling or extracting turbine on the basis of its me- chanical and geometric parameters as well as the characteristics of the interacting flow. This model results from the combination of two theories: the **Blade** **Element** Theory and the **Momentum** Theory. The former was introduced by William Froude [ 10 ] in 1878 to study the behavior of turbines from a local point of view. In this framework, the turbine **blade** is cut into sections, the **blade** elements, each of them being approx- imated by a planar model. This approach results in expressions of the forces exerted on the **blade** **element**, as functions of the flow characteristics and **blade** geometry. The fundamental quantities of this model are two experimental coefficients (usually denoted by CL and CD), called lift and drag coefficients respectively, which account for the forces in the cross-section as functions of the angle of attack, i.e. the relative angle between the rotating **blade** and flow. The results are then integrated along the **blade** to obtain global values.

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Key words. Turbine design, **Blade** **Element** **Momentum** theory, Computational Fluid Dynamics, Geometry Modeling, Wind Turbine Aerodynamics, Fluid–Structure Interaction
AMS subject classifications. 76G25, 76M99, 65Z05
1. Introduction. The **Blade** **Element** **Momentum** (BEM) theory is a model used to evaluate the performance of a propelling or extracting turbine on the basis of its me- chanical and geometric parameters as well as the characteristics of the interacting flow. This model results from the combination of two theories: the **Blade** **Element** Theory and the **Momentum** Theory. The former was introduced by William Froude [ 10 ] in 1878 to study the behavior of turbines from a local point of view. In this framework, the turbine **blade** is cut into sections, the **blade** elements, each of them being approx- imated by a planar model. This approach results in expressions of the forces exerted on the **blade** **element**, as functions of the flow characteristics and **blade** geometry. The fundamental quantities of this model are two experimental coefficients (usually denoted by C L and C D ), called lift and drag coefficients respectively, which account

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In the present study, a passive twist control is considered as a potential way to improve the overall flight efficiency for proprotor of Micro Air Vehicle (MAV). This paper will focus on the aerody- namic performance and deformation behaviour of a flexible laminate **blade**. Incorporated with a database of airfoil characteristics, **Blade** **Element** **Momentum** Theory (BEMT) is implemented for performance prediction of proprotor at low Reynolds numbers. The preliminary procedure is based on finding optimum twist distributions for hover and forward flight, but keeping a given chord dis- tribution. A numerical model is developed using a combination of aerodynamic model based on BEMT, and structural model based on anisotropic beam finite **element**, in order to evaluate the coupled structural and the aerodynamic characteristics of the deformable proprotor **blade**. The numerical model - Fluid Structure Interaction (FSI) was then validated by means of shape recon- struction from LDS (Laser Displacement Sensor) outputs. It can be concluded that the proposed experiment technique is capable of providing a predictive and reliable data in **blade** geometry and performance for rotor mode. The FSI approach is also valid as a reliable tool for designing and analyzing the MAV proprotor made of composite material.

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In the present study, a passive twist control is considered as a potential way to improve the overall flight efficiency for proprotor of Micro Air Vehicle (MAV). This paper will focus on the aerody- namic performance and deformation behaviour of a flexible laminate **blade**. Incorporated with a database of airfoil characteristics, **Blade** **Element** **Momentum** Theory (BEMT) is implemented for performance prediction of proprotor at low Reynolds numbers. The preliminary procedure is based on finding optimum twist distributions for hover and forward flight, but keeping a given chord dis- tribution. A numerical model is developed using a combination of aerodynamic model based on BEMT, and structural model based on anisotropic beam finite **element**, in order to evaluate the coupled structural and the aerodynamic characteristics of the deformable proprotor **blade**. The numerical model - Fluid Structure Interaction (FSI) was then validated by means of shape recon- struction from LDS (Laser Displacement Sensor) outputs. It can be concluded that the proposed experiment technique is capable of providing a predictive and reliable data in **blade** geometry and performance for rotor mode. The FSI approach is also valid as a reliable tool for designing and analyzing the MAV proprotor made of composite material.

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such as the Darrieus-type VAWT. The code is used to determine, at specified operational conditions, aero-dynamic forces and power output of VAWTs of any **blade** geometry. Wind speed can vary with height above ground according to a power law. The program output consists of the local- induced velocities, the local Reynolds numbers and angle of attack, the **blade** loads, and the azimuthal torque and power coeﬃcient data. Each of these is calculated separately for the upwind and downwind halves of the rotor. The numerical models used by the program have been validated

Moreover, significant unsteady effects are usually detected when the vapor volume becomes significant in the machinery. Experi- mental results point out two main types of cavitation instabilities: a self-oscillation behavior of cavitation sheets, whose mechanism was studied in cavitation tunnels and analyzed by many authors (including Kubota et al. [ 1 ] and Le et al. [ 2 ]), and a coupling between the cavitation areas in the different **blade** to **blade** chan- nels. This second type of instability consists for example of differ- ent sizes of sheet cavities on the blades. Such dissymmetry can also be steady in the inducer rotating frame or unsteady, leading in this case to the so-called super or subsynchronous rotating cavitation, whether the dissymmetry rotates faster or slower than the inducer.

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stress **blade** design has reduced maximum stress by 37% and improved efficiency, pressure ratio and mass flow rate by 1.35%, 1.54%, and 1.41% respectively.
In the work carried out by Deng, Guo et al. [75], frequency constraints were implemented within the rotational speed varying from 95% to 105% that means within this speed no mode were allowed in the engine running range. In this work, multi-objective including enhancement in efficiency at design point and the slope of adiabatic efficiency, at the point 95% of the design mass flow rate to redesign a transonic fan **blade** were considered. A total of nine (9) constraints were considered: one constraint for choke margin, one for mass flow rate, one for pressure ratio, two for von-Mises stress and three for dynamic frequency modes. Stress analysis was carried out at the red line speed (engine maximum speed). The commercial software Isight was used for the optimization. The optimization process was based on first DoE database construction from high- fidelity computations (CFD/FEA) to initialize a Kriging surrogate model. After that Non- dominated Sorting Genetic Algorithm (NSGA II) was used to obtain Pareto front. The design optimization achieved a 0.2% efficiency gain at design point and a 0.67% efficiency improvement at 95% of the cruise mass flow rate condition.

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ABSTRACT
This work focuses on numerical simulations of flows in **blade** internal cooling system. Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS) approaches are com- pared in a typical **blade** cooling related problem. The case is a straight rib-roughened channel with high blockage ratio, com- puted and compared for both a periodic and full spatial domains. The configuration was measured at the Von Karman Institute (VKI) using Particle Image Velocimetry (PIV) in near gas tur- bine operating conditions. Results show that RANS models used fail to predict the full evolution of the flow within the channels where massive separation and large scale unsteady features are evidenced. In contrast LES succeeds in reproducing these com- plex flow motions and both mean and fluctuating components are clearly improved in the channels and in the near wall region. Periodic computations are gauged against the spatial computa- tional domain and results on the heat transfer problem are ad- dressed.

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These results indicate the event observed on probe 46, associated with the spectrum hump around 1.3 kHz, corresponds to an unsteady tip separation.. The corresponding Strouhal number, ca[r]

city has been realised most forcefully in the work of Ridley Scott, its fullest expression generally conceded to be **Blade** Runner (McArthur, 32).
In fact, the only way time is ever expressed is through the character of Roy Batty; through his blueish nails, his slow loss of control over his limbs, and his natural death due to his reaching the end of his four-year lifespan. Paradoxically, the lack of time and the replicants' quest to get a longer lifespan is central to the film in which night succeeds to night. As it is impossible to gain any sense of time throughout the film, a growing impression that the diegesis simply operates outside of time in a quite surreal manner is developed as the plot unfolds. In fact, the lack of representation of time insidiously paralyses the narrative as it is both absent and distorted into one slow, long and starless night (although a careful viewer will remember that stars are shown once in the film, like a sort of surreal manifestation, after Batty has murdered Tyrell and is returning to street level by using an elevator with a glass roof). Time, one of the film's obsessions, is the last of the film's oneiric lures, it is abstract, suspended, but also eternal within the bounds of the city.

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Design of GaN meta-holograms. Meta-holograms that were used for the demonstration of metasurface orbital angular **momentum** (OAM) holography were realized by disposing Gallium Nitride (GaN) nanopillars with designed structural parameters to introduce proper forward scattering phase and amplitude at de ﬁned positions along the interface. The amplitude and phase responses are related to the radius of nanopillar meta-atoms with a constant height of 1 µm. The sub- wavelength lattice constant in meta-holograms is 340 nm, which is suf ﬁciently small to avoid the diffraction effect in both air and substrate. To quantify the phase retardation of light transmitted through GaN nanopillars, electromagnetic simu- lations of subwavelength nanopillars arranged in a square lattice were performed using the FDTD. We specify the dispersion of GaN nanopillars from ellipsometry measurements realized on epitaxially grown GaN thin-ﬁlm on a double-side

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Figure 1: Sketches of cavitation patterns and performance evolu- tion as the cavitation number decreases in a four-**blade** inducer [ 9 ].
configuration appears with alternatively one short and one long cavity. For a lower cavitation parameter, just above breakdown, rotating cavitation can be identified: unbalanced attached cavities are observed in the different channels, their distribution rotating faster than the inducer. Finally near the breakdown of the inducer, a steady and balanced flow pattern with fully developed cavitation is observed.

A finite element model (FEM) of the Active Rotor was used to predict the stresses in the composite spar due to centrifugal loads, the blade tip deflection availa[r]

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Figure C-1: Canonical Boundary Layer Edge Velocity Distribution - Canonical boundary layer edge velocity distribution defined to characterize the effects from shape pa[r]

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This research hinges on three aspects of lean methodology: enterprise and department level value stream mapping, management of improvement initiatives, and the design of a dedic[r]

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7. Conclusion et travaux futurs
Dans cette étude, un outil nommé **BLADE** est présenté. **BLADE** permet d’obtenir une recommandation sur la blockchain à utiliser étant donné un ensemble d’exigences et de préférences utilisateurs. Pour cela, un panel pertinent de blockchains ainsi que de critères relatifs à la qualité d’un système (norme ISO 25010) ont été sélectionnés pour créer une base de connaissance, puis une liste de termes permettant à un utilisateur de soumettre ses préférences et exigences quant aux critères choisis pour la décision a été choisie. Le processus de décision est ensuite présenté en détail, de l’envoi d’entrées dans celui-ci à la recommandation par le biais de TOPSIS. Une implémentation de **BLADE** incluant ce processus de décision est présentée. Elle permet notamment la saisie aisée des exigences au travers d’une plateforme web. Enfin, le processus de décision est validé à travers cas d’étude de gestion de chaîne logistique et montré que **BLADE** est capable de recommander une blockchain alignée aux besoins de l’utilisateur. Une implémentation de l’outil est disponible sur Github 16 ainsi qu’en accès direct, en ligne 17 .

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It is well known that due to geometric reasons, the ef- fective wind velocity vector varies both, in magnitude and direction, along a wind turbine **blade**. An optimum perfor- mance — assuming constant airfoil section throughout the **blade** — would require the exact same relative orientation between the local wind velocity vector and the corresponding cross-section of the **blade**. As an attempt to reach s-uch opti- mum performance, modern blades are produced with a phys- ical twist, which may correspond to the theoretically ideal value.

‘Synchronous’ or ‘engine-ordered’ **blade** response occurs when a blade’s vibration frequency is an integer multiple of the engine rotation speed. Synchronous vibrations can be caused by mechanical effects, such as residual unbalance of the rotors and non-concentric casings, as well as aerody- namic effects, such as irregular pressure distributions within the airflow due to the engine intake geometry and wakes produced by upstream stators [5]. ‘Asynchronous’ response occurs when the **blade** response frequency is a non-integer multiple of the assembly rotation speed. This response condition can be caused either by flutter, a rotating stall, or by acoustic resonance [5].

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Finally, to confirm EM simulation results, real data experiments are presented in a last part. The experiment involves a three **blade** helicopter landed on an airport and radiated by an interference source. A 2x2 square array GNSS right hand circularly polarized (RHCP) antenna is placed close to the helicopter under the main rotor. The jammer is a RHCP L-band wave located above the helicopter in order to cross the blades path. The experiment has been conducted with a Continuous Wave (CW) source with and without **blade** rotation.

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L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]