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1
Davis, M. J. „Microvascular control of capillary pressure during increases in local arterial and venous pressure“. American Journal of Physiology-Heart and Circulatory Physiology 254, Nr. 4 (01.04.1988): H772—H784. http://dx.doi.org/10.1152/ajpheart.1988.254.4.h772.
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The extent to which capillary hydrostatic pressure might be protected from increases in local arterial and venous pressure was examined in the wing microcirculation of unanesthetized pallid bats (Antrozous pallidus). Arterial inflow and venous outflow pressures to the wing were elevated using a box technique to increase pressure around the body of the animal in steps of 12 mmHg between 0 and +60 mmHg for 3-min periods. During this time, hydrostatic pressure, diameter, and red cell velocity in single microvessels were continuously recorded. All branching orders of arterioles constricted significantly during increases in box pressure (Pb), while capillaries and venules dilated. First-order arteriole and venule pressures increased 1:1 with Pb. Capillary pressures increased by only a fraction of Pb up to +36 mmHg, but at higher Pb, the change in capillary pressure was equivalent to the change in Pb. Calculations of vascular resistance indicate that changes in both pre- and postcapillary resistance in this tissue act to prevent increases in capillary pressure during moderate, but not during large, increases in arterial and venous pressure.
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Sato, M., und A. Azuma. „The flight performance of a damselfly Ceriagrion melanurum Selys“. Journal of Experimental Biology 200, Nr. 12 (01.01.1997): 1765–79. http://dx.doi.org/10.1242/jeb.200.12.1765.
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The local circulation method was applied to the free forward flight of the damselfly Ceriagrion melanurum Selys. The kinematic data used in the calculations were obtained by analyzing video-taped images of damselflies in free flight in a transparent container. The inclination of the stroke plane was smaller and the flapping amplitude was larger than those of dragonflies reported in other studies on odonate flight. However, the phase shift between the fore- and hindwings agreed with none of the previously reported patterns for damselflies: the forewings lead the hindwings by approximately a quarter-period. The calculated forces were within the expected range of error. The muscle-mass-specific power was between 40 and 80 W kg-1. The vorticity distribution of trailing and shed vortices in the wake was also analyzed. Strong trailing vortices were observed at the wing tips, whereas shed vortices were concentrated near the wing root as the stroke switched direction.
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Гребеников, А. Г., und Д. Ю. Жиряков. „АНАЛІЗ СИЛ ФУНКЦІОНУВАННЯ ВІД’ЄМНОЇ ЧАСТИНИ КРИЛА ЛІТАКА ТРАНСПОРТНОЇ КАТЕГОРІЇ“. Open Information and Computer Integrated Technologies, Nr. 89 (23.03.2021): 4–20. http://dx.doi.org/10.32620/oikit.2020.89.01.
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Each experimental design department has experience in determining design and operational loads for a given type of aircraft. The reliability of the data on the loading of a particular structural element determines the success of the aircraft being created. This is often confidential information. Much work has been investigated to improve the fatigue life of wing structural elements. With the development of integrated design methods, aircraft structure design can be performed in the shortest time, and with high technical excellence. In most cases, the fatigue life of wing elements is determined from the nominal stresses in the element. For a longitudinal structure set, it is customary to perform fatigue calculations directly using normal stresses in the element. For a more detailed specification of the fatigue life, it is necessary to have a general and local stress-strain state of a given structure. A feature of the work is to analyze the spectrum of loads acting on the wing console during a typical flight. The influence of high-lift devises (slats, flaps) on the shear forces and torque moment of the wing was analyzed. It has been shown that with the extensions high-lift devices, there is a significant increase in torque. These articles will make it possible to obtain the stress distribution of the detachable part of the wing under all operating modes. This, in turn, leads to a more thorough prediction of fatigue life. Since some operating loads can significantly change the distribution of the stress-strain state in the design element, and in turn change the fatigue life. The structural elements of the wing, in particular the attachment points for the high-lift devices, operate in a complex-stressed state. This complicates the process of predicting the fatigue life of these elements. To obtain a competitive aircraft, it is necessary to develop new methods of wing design with widespread use of integrated systems. This will contribute to obtaining a more optimal and perfect wing design
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Ruban, A. I., T. Bernots und M. A. Kravtsova. „Linear and nonlinear receptivity of the boundary layer in transonic flows“. Journal of Fluid Mechanics 786 (30.11.2015): 154–89. http://dx.doi.org/10.1017/jfm.2015.587.
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In this paper we analyse the process of the generation of Tollmien–Schlichting waves in a laminar boundary layer on an aircraft wing in the transonic flow regime. We assume that the boundary layer is exposed to a weak acoustic noise. As it penetrates the boundary layer, the Stokes layer forms on the wing surface. We further assume that the boundary layer encounters a local roughness on the wing surface in the form of a gap, step or hump. The interaction of the unsteady perturbations in the Stokes layer with steady perturbations produced by the wall roughness is shown to lead to the formation of the Tollmien–Schlichting wave behind the roughness. The ability of the flow in the boundary layer to convert ‘external perturbations’ into instability modes is termed the receptivity of the boundary layer. In this paper we first develop the linear receptivity theory. Assuming the Reynolds number to be large, we use the transonic version of the viscous–inviscid interaction theory that is known to describe the stability of the boundary layer on the lower branch of the neutral curve. The linear receptivity theory holds when the acoustic noise level is weak, and the roughness height is small. In this case we were able to deduce an analytic formula for the amplitude of the generated Tollmien–Schlichting wave. In the second part of the paper we lift the restriction on the roughness height, which allows us to study the flows with local separation regions. A new ‘direct’ numerical method has been developed for this purpose. We performed the calculations for different values of the Kármán–Guderley parameter, and found that the flow separation leads to a significant enhancement of the receptivity process.
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FEDOROV, A. V., N. D. MALMUTH und V. G. SOUDAKOV. „Supersonic scattering of a wing-induced incident shock by a slender body of revolution“. Journal of Fluid Mechanics 585 (07.08.2007): 305–22. http://dx.doi.org/10.1017/s0022112007006714.
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The lift force acting on a slender body of revolution that separates from a thin wing in supersonic flow is analysed using Prandtl–Glauert linearized theory, scattering theory and asymptotic methods. It is shown that this lift is associated with multi-scattering of the wing-induced shock wave by the body surface. The local and global lift coefficients are obtained in simple analytical forms. It is shown that the total lift is mainly induced by the first scattering. Contributions from second, third and higher scatterings are zero in the leading-order approximation. This greatly simplifies calculations of the lift force. The theoretical solution for the flow field is compared with numerical solutions of three-dimensional Euler equations and experimental data at free-stream Mach number 2. There is agreement between the theory and the computations for a wide range of shock-wave strength, demonstrating high elasticity of the leading-order asymptotic approximation. Theoretical and experimental distributions of the cross-sectional normal force coefficient agree satisfactorily, showing robustness of the analytical solution. This solution can be applied to the moderate supersonic (Mach numbers from 1.2 to 3) multi-body interaction problem for crosschecking with other computational or engineering methods.
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Brazier, Jean-Philippe, Frédéric Moens und Philippe Bardoux. „Spatial Stability Analysis of a Flap Side Edge Vortex“. International Journal of Aeroacoustics 4, Nr. 1-2 (Januar 2005): 37–47. http://dx.doi.org/10.1260/1475472053730066.
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The flap side edge vortex is suspected to contribute to aerodynamic noise generation. Using a temporal stability analysis, Khorrami and Singer have shown that unstable modes could exist in this vortex. Due to the convective nature of this instability, a spatial analysis is more suitable. This is the subject of the present work. The mean flow past a 2D wing with a half-span flap has been computed with a steady 3D Navier-Stokes code. Then, local linear stability calculations are performed in several planes perpendicular to the vortex axis. The vortex is assumed axisymmetric and modelled with Batchelor's analytical vortex. Using Gaster's relation, the spatial amplification rate is calculated, giving by integration the relative amplitude of the fluctuations. Some low-frequency fluctuations are seen to be preferentially amplified by the vortex, but the amplifications remain small, so that this mechanism alone should not produce important noise in this particular configuration, where the flap deflection angle is moderate.
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Крашаница, Юрий Александрович, und Дмитрий Юрьевич Жиряков. „Аэродинамический профиль в трансзвуковом потоке газа“. Aerospace technic and technology, Nr. 2 (28.04.2021): 20–27. http://dx.doi.org/10.32620/aktt.2021.2.03.
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The subject of investigation in this article is transonic flow. This is a condition in which local speeds of sound are appears on the wing surface, even at the subsonic speed of the nonturbulent flow. As a result, at a certain speed of the incoming flow, the flow regime around the aerodynamic surface will change sharply, which in turn changes the aerodynamic characteristics. Aerodynamic surfaces of the most transport category airplane experience transonic airflow during flight. The goal of the investigation is to study aerodynamic characteristics using numerical methods. The use of numerical methods in the design of aircraft structures is used more and more often to determine the optimal parameters for given operating conditions. This contributes to obtaining a more optimal and perfect design. In this article, we carried out a numerical analysis of the aerodynamic characteristics of airfoils in the transonic flow case using the CAE system CFD ANSYS. As a result of the research, the distributions of the pressure coefficients over the profile surface were obtained. The nature of the flow is obtained, which is similar to the picture of the pressure coefficients for transonic flow in the published sources of this topic. In the area of the middle of the profile, a shock-wave is observed. As a result, the flow around the airfoil changes, which contributes to a change in aerodynamic characteristics. The behavior of the aerodynamic drag and lift coefficients depending on the speed of the Mach number is considered. Also, the position of the center of pressure was analyzed at various velocities of the nonturbulent flow. The calculation was carried out at the cruising altitude of a medium-range aircraft of 11 km. For the calculations, we used the characteristics of the air temperature, the pressure of a given height from the table of the standard atmosphere.
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Secco, Ney Rafael, und Bento Silva de Mattos. „Artificial neural networks to predict aerodynamic coefficients of transport airplanes“. Aircraft Engineering and Aerospace Technology 89, Nr. 2 (06.03.2017): 211–30. http://dx.doi.org/10.1108/aeat-05-2014-0069.
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Purpose Multidisciplinary design frameworks elaborated for aeronautical applications require considerable computational power that grows enormously with the utilization of higher fidelity tools to model aeronautical disciplines like aerodynamics, loads, flight dynamics, performance, structural analysis and others. Surrogate models are a good alternative to address properly and elegantly this issue. With regard to this issue, the purpose of this paper is the design and application of an artificial neural network to predict aerodynamic coefficients of transport airplanes. The neural network must be fed with calculations from computational fluid dynamic codes. The artificial neural network system that was then developed can predict lift and drag coefficients for wing-fuselage configurations with high accuracy. The input parameters for the neural network are the wing planform, airfoil geometry and flight condition. An aerodynamic database consisting of approximately 100,000 cases calculated with a full-potential code with computation of viscous effects was used for the neural network training, which is carried out with the back-propagation algorithm, the scaled gradient algorithm and the Nguyen–Wridow weight initialization. Networks with different numbers of neurons were evaluated to minimize the regression error. The neural network featuring the lowest regression error is able to reduce the computation time of the aerodynamic coefficients 4,000 times when compared with the computing time required by the full potential code. Regarding the drag coefficient, the average error of the neural network is of five drag counts only. The computation of the gradients of the neural network outputs in a scalable manner is possible by an adaptation of back-propagation algorithm. This enabled its use in an adjoint method, elaborated by the authors and used for an airplane optimization task. The results from that optimization were compared with similar tasks performed by calling the full potential code in another optimization application. The resulting geometry obtained with the aerodynamic coefficient predicted by the neural network is practically the same of that designed directly by the call of the full potential code. Design/methodology/approach The aerodynamic database required for the neural network training was generated with a full-potential multiblock-structured code. The training process used the back-propagation algorithm, the scaled-conjugate gradient algorithm and the Nguyen–Wridow weight initialization. Networks with different numbers of neurons were evaluated to minimize the regression error. Findings A suitable and efficient methodology to model aerodynamic coefficients based on artificial neural networks was obtained. This work also suggests appropriate sizes of artificial neural networks for this specific application. We demonstrated that these metamodels for airplane optimization tasks can be used without loss of fidelity and with great accuracy, as their local minima might be relatively close to the minima of the original design space defined by the call of computational fluid dynamics codes. Research limitations/implications The present work demonstrated the ability of a metamodel with artificial neural networks to capture the physics of transonic and subsonic flow over a wing-fuselage combination. The formulation that was used was the full potential equation. However, the present methodology can be extended to model more complex formulations such as the Euler and Navier–Stokes ones. Practical implications Optimum networks reduced the computation time for aerodynamic coefficient calculations by 4,000 times when compared with the full-potential code. The average absolute errors obtained were of 0.004 and 0.0005 for lift and drag coefficient prediction, respectively. Airplane configurations can be evaluated more quickly. Social implications If multidisciplinary optimization tasks for airplane design become more efficient, this means that more efficient airplanes (for instance less polluting airplanes) can be designed. This leads to a more sustainable aviation. Originality/value This research started in 2005 with a master thesis. It was steadily improved with more efficient artificial neural networks able to handle more complex airplane geometries. There is a single work using similar techniques found in a conference paper published in 2007. However, that paper focused on the application, i.e. providing very few details of the methodology to model aerodynamic coefficients.
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AZUMA, AKIRA, SOICHI AZUMA, ISAO WATANABE und TOYOHIKO FURUTA. „Flight Mechanics of a Dragonfly“. Journal of Experimental Biology 116, Nr. 1 (01.05.1985): 79–107. http://dx.doi.org/10.1242/jeb.116.1.79.
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The steady slow climbing flight of a dragonfly, Sympetrum frequens, was filmed and analysed. By using the observed data, the mechanical characteristics of the beating wings were carefully analysed by a simple method based on the momentum theory and the blade element theory, and with a numerical method modified from the local circulation method (LCM), which has been developed for analysing the aerodynamic characteristics of rotary wings. The results of calculations based on the observed data show that the dragonfly performs low speed flight with ordinary airfoil characteristics, instead of adopting an abnormally large lift coefficient. The observed phase advance of the hindwing, Δδ1 ≃ 80° can be fully explained by the present theoretical calculation. Similarly, the spanwise variation of the airloading and the time variations of the horizontal force, vertical force, pitching moment and torque or power can be definitely estimated within a reasonable range of accuracy in comparison with the flight data. The distribution of loading between the fore and hind pairs of wings is also clarified by the calculations.
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Cao, Xiao, Pei Pei Peng, Hai Zhou und Xu Cheng. „Technology of Wind Power Forecasting Accuracy Assessment and Curtail Quantity Estimation with Power Capacity Limited“. Applied Mechanics and Materials 672-674 (Oktober 2014): 280–85. http://dx.doi.org/10.4028/www.scientific.net/amm.672-674.280.
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Eastern Inner Mongolia is by now one of the areas with the most rapid development of wind power in China. There exists mismatching between wind power supply ability and level of local economy. Thus, wind farms will be inevitability partly involved in peak shaving. The researches on accuracy assessment on wind power forecasting and estimation of power rationing quantity on condition of wind power curtail contribute to provide effective data evidence for scheduling and dispatching operations. In this paper, a new method for accuracy assessment on wind power forecasting and estimation of power rationing quantity through calculating theoretical power were presented first. Then, the algorithm of theoretical power calculation was presented. Case study proved the feasibility and effectiveness of the method. The conclusion indicated that the method has feasible and objective mean for accuracy assessment on wind power forecasting on condition of wind power curtail, which can provide objective and accurate theoretical and data support for dispatching and scheduling operations on condition of wind power curtail.
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Baïri, Abderrahmane, David San Martin, Iken Baïri, Kemi Adeyeye, Kaiming She, Ali Hocine, Nacim Alilat et al. „Aerodynamics in the open channel of the Sistan-type wind-mill with vertical axis wind turbine“. International Journal of Numerical Methods for Heat & Fluid Flow 26, Nr. 8 (07.11.2016): 2298–309. http://dx.doi.org/10.1108/hff-06-2015-0226.
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Purpose The purpose of this paper is to examine the details of the air mass flow and aerodynamical phenomena across a channel containing a large vertical axis wind turbine. The considered model reproduces as closely as possible the real assembly of the Sistan-type wind-mill whose top is open. The technical results of this work could be used for the restoration and operation of this assembly whose historical and architectural values are recognized. Design/methodology/approach Several inlet velocities into the channel are considered, taking into account the possible local wind resources. Calculations corresponding to Reynolds number varying between 8×105 and 4×106 are made by means of the finite volume method and turbulence is treated with the realizable k-ε model. The mesh consists of a fixed part associated to the contour of the channel, interfaced with a moving one linked to the turbine itself, equipped with nine partly filled wings. Findings The relative pressure and velocity fields are presented for various dynamic and static conditions. Calculation results clearly show that the vortex phenomena present in some cases are not a source of degradation of the wind turbine’s aerodynamical performances, given its location, intensity and rotation direction. Particular attention is devoted to the air mass flow and its distribution between the inlet and the outlet sections of the channel. Originality/value The present work provides technical information useful to consider the restoration and modernization of this installation whose architecture and technical performance are very interesting. This survey complements a previous one examining the aerodynamical phenomena occurring in a modified version of this assembly with a closed top channel.
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R, Sridhar, Boopathi C.S, Deepanjali Das, Sakshi Agrawal und Hardik Choubisa. „An ingenious invasive weed optimization (IWO) aided maximum power tracking for partially shaded photovoltaic array“. Indonesian Journal of Electrical Engineering and Computer Science 15, Nr. 2 (01.08.2019): 543. http://dx.doi.org/10.11591/ijeecs.v15.i2.pp543-553.
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<p>The inborn non-direct power voltage trademark bends concerning barometrical temperature and light makes the photovoltaic (PV) source a discontinuous one. Maximum power point (MPPT) following is a procedure through which most extreme accessible power is yielded from the PV for the given purpose of time. Prior, the customary MPPT methods, for example, perturb and observe, incremental conductance, hill climbing and so forth strategies were utilized and these methods stayed inadequate when the PV source is partially shaded (PS), since amid (PS) the power voltage (P-V) bends show different power crests. There wins each possibility that the ordinary calculations will stall out to the local maximum point and the global maximum point won't be accomplished and in this way control misfortune is brought about. The metaheuristic calculations give better arrangements however confront the downside of high weight on processor and enormous number of information prerequisites. In this way, in this paper, a novel calculation in light of invasive weed optimisation (IWO) technique is utilized to locate the Global maximum point for MPPT under in part shaded condition and it is contrasted and its nearby partner differential evolution(DE) MPPT algorithm and furthermore with the very much settled in perturb and observe (P&O) calculation. The proposed calculation is actualized in MATLAB condition and tried on a 3-board PV cluster arrangement of 150 W. The flexibility of the calculation is tried through various experiments and the outcomes demonstrate the effectiveness and exactness of the proposed calculation in finding the global maximum point.</p>
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Котов, Геннадий Викторович, und Сергей Павлович Фисенко. „Semi-empirical model of calculating the parameters of the actual zone of contamination when setting up water curtains“. Journal of Civil Protection 4, Nr. 4 (20.11.2020): 424–32. http://dx.doi.org/10.33408/2519-237x.2020.4-4.424.
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Purpose. The development of a semi-empirical model of calculating the effect of water curtains on the propagation of hazardous chemical vapors with wind flow from a local source of release (spillage).
Methods. Laboratory studies of the absorption of gaseous impurities by moving water drops. Field tests to determine the parameters of the actual contamination zone in the conditions of ammonia and chlorine spills with free spread of impurities and in the conditions of setting up water curtains. Fuller's method. Galerkin's method. Method of straight lines. Mathematical modeling. Three-dimensional solution of the turbulent diffusion equation. Inter- and extrapolation estimates. Semi-empirical calculations using the results of laboratory research, field tests and mathematical modeling.
Findings. The absorption capacity and transmittance index of water curtains created with the use of a hose spray are calculated in case of the propagation of ammonia and chlorine with a wind flow from the source of emission (spillage). A formula is proposed for calculating the numerical density of the impurity taking into account the transmittance index and fractional impurities not absorbed by the water curtain. The boundaries of the actual contamination zone were determined with the free spread of ammonia and chlorine from the surface of the strait and under the conditions of setting up water curtains. A method is proposed for calculating the depth of the actual contamination zone using the curtain transmittance. A semi-empirical model has been developed for calculating the effect of water curtains on the propagation of hazardous chemical vapors with a wind flow from a local source of release (spillage).
Application field of research. Prediction of the parameters of the actual contamination zone during the release (spillage) of a hazardous chemical during the rescue operations.
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Alford, Matthew H. „Global Calculations of Local and Remote Near-Inertial-Wave Dissipation“. Journal of Physical Oceanography 50, Nr. 11 (November 2020): 3157–64. http://dx.doi.org/10.1175/jpo-d-20-0106.1.
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AbstractGlobal estimates are presented of the fraction q of wind-generated near-inertial wave power available for local turbulent dissipation under the assumption that modes 1–3 propagate “far” and the higher modes remain to eventually break. Using climatological stratification profiles and mixed layer depth, the modal distribution of near-inertial energy flux is computed following Gill's classic 1984 work by projecting a slab flow in the mixed layer onto the dynamical modes. Global maps and zonal-mean profiles are presented, which show a global-mean value of q = 0.63 and 0.75 for winter and summer profiles, respectively. The simplicity of the calculation makes it of potential use in parameterizations of near-inertial breaking in climate simulations.
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Harutyunyan, G., M. Steffen, A. Mott, E. Caffau, G. Israelian, J. I. González Hernández und K. G. Strassmeier. „3D non-LTE corrections for Li abundance and 6Li/7Li isotopic ratio in solar-type stars“. Astronomy & Astrophysics 618 (Oktober 2018): A16. http://dx.doi.org/10.1051/0004-6361/201832852.
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Context. Convective motions in solar-type stellar atmospheres induce Doppler shifts that affect the strengths and shapes of spectral absorption lines and create slightly asymmetric line profiles. One-dimensional (1D) local thermodynamic equilibrium (LTE) studies of elemental abundances are not able to reproduce this phenomenon, which becomes particularly important when modeling the impact of isotopic fine structure, like the subtle depression created by the 6Li isotope on the red wing of the Li I resonance doublet line. Aims. The purpose of this work is to provide corrections for the lithium abundance, A(Li), and the 6Li/7Li isotopic ratio that can easily be applied to correct 1D LTE lithium abundances in G and F dwarf stars of approximately solar mass and metallicity for three-dimensional (3D) and non-LTE (NLTE) effects. Methods. The corrections for A(Li) and 6Li/7Li are computed using grids of 3D NLTE and 1D LTE synthetic lithium line profiles, generated from 3D hydro-dynamical CO5BOLD and 1D hydrostatic model atmospheres, respectively. For comparative purposes, all calculations are performed for three different line lists representing the Li I λ670.8 nm spectral region. The 3D NLTE corrections are then approximated by analytical expressions as a function of the stellar parameters (Teff, log ℊ, [Fe/H], ν sin i, A(Li), 6Li/7Li). These are applied to adjust the 1D LTE isotopic lithium abundances in two solar-type stars, HD 207129 and HD 95456, for which high-quality HARPS observations are available. Results. The derived 3D NLTE corrections range between −0.01 and +0.11 dex for A(Li), and between −4.9 and −0.4% for 6Li/7Li, depending on the adopted stellar parameters. We confirm that the inferred 6Li abundance depends critically on the strength of the Si I 670.8025 nm line. Our findings show a general consistency with recent works on lithium abundance corrections. After the application of such corrections, we do not find a significant amount of 6Li in any of the two target stars. Conclusions. In the case of 6Li/7Li, our corrections are always negative, showing that 1D LTE analysis can significantly overestimate the presence of 6Li (up to 4.9% points) in the atmospheres of solar-like dwarf stars. These results emphasize the importance of reliable 3D model atmospheres combined with NLTE line formation for deriving precise isotopic lithium abundances. Although 3D NLTE spectral synthesis implies an extensive computational effort, the results can be made accessible with parametric tools like the ones presented in this work.
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Olenkov, V., und N. Tazeev. „CALCULATION OF WIND LOADS TAKING INTO ACCOUNT LOCAL CHANGES IN WIND SPEED IN URBAN DEVELOPMENT AREA“. Bulletin of South Ural State University series "Construction Engineering and Architecture" 19, Nr. 4 (2019): 5–17. http://dx.doi.org/10.14529/build190401.
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Soliman, Mohamed Hassan, Bassel I. Nesser und Krzysztof Pytel. „Local benefits factored in utility scale wind energy for a remote location“. New Trends in Production Engineering 2, Nr. 1 (01.10.2019): 549–54. http://dx.doi.org/10.2478/ntpe-2019-0059.
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Abstract The publication presents the results of analysis of possible local benefits factored in utility scale wind energy for a remote location. Electricity is one of the most vital problems on the Earth, thus utility scale wind and solar energy devices are boosting economic development. Energy demand is constantly increasing, despite efforts to ensure the energy efficiency of devices. People are looking for more energy and electricity to consume. Although wind energy is still being researched and improved, modern generation of wind energy is becoming more and more effective and desirable. This publication presents an effective solution to this issue. It deals with the generation of green environment friendly electricity from wind turbine. The genuine idea is to provide energy for remote location using onshore wind turbines. An analysis of the demand for energy at a remote location and electricity consumption was made to provide preliminary calculations of the wind farm. The number of required turbines is determined taking into account all related factors. A specific wind turbine has been selected and proposed to provide the necessary location with the necessary amount of energy. The analysis carried out showed that the produced energy is environment friendly since there is no carbon dioxide emission.
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Ma, Xin Wei, Sen Zeng, Chong Hai Dong, Zhi Yu und Guan Qi Huang. „Design of Assembled Post-Tensioned Prestressed Reactive Powder Concrete Wind Turbine Tower“. Advanced Materials Research 1055 (November 2014): 38–43. http://dx.doi.org/10.4028/www.scientific.net/amr.1055.38.
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This paper proposes a new type of assembled post-tensioned prestressed reactive powder concrete (RPC) turbine tower structure. It includes the structure design of 200kW wind turbine tower according to the specifications, calculation of loading combinations and internal force, checking calculation of bearing capacity, prestressed concrete design and calculation of reinforcement. Local stress applied on the structure is analyzed by the finite element software of ANSYS, and the calculation results show that the bearing capacity calculation of RPC tower satisfies the requirements, and it is economical comparing with the traditional steel structures.
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Uchida, Takanori, und Keiji Araki. „Reproduction of Local Strong Wind Area Induced in the Downstream of Small-Scale Terrain by Computational Fluid Dynamic (CFD) Approach“. Modelling and Simulation in Engineering 2019 (04.12.2019): 1–12. http://dx.doi.org/10.1155/2019/7378315.
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In this research, the computational fluid dynamic (CFD) approach was applied for the solution of the problems of local strong wind areas in railway fields, and the mechanism of wind generation was discussed. The problem of local wind occurring on a railway line in winter was taken up in this research. A computational simulation for the prediction of wind conditions by large-eddy simulation (LES) was implemented, and it was clarified that local strong wind areas are mainly caused by separated flows originating from small-scale terrain positioned at its upstream (at approximately 180 m above sea level). Meanwhile, the effects of the size of the calculation area and spatial grid resolution on the result of calculation and the effect of atmospheric stability were also discussed. It was clarified that in order to simulate the air flow characteristic of the separated flow originating from the small-scale terrain (at an altitude of approximately 180 m) targeted in the present research, approximately 10 m of spatial resolution of computational cell in the horizontal direction is required. In addition, the effect of stable stratification on the flow was also examined. As a result, lee waves were excited at the downstream of the terrain over time in the case of stably stratified flow (Fr = 1.0). The reverse-flow region lying behind the terrain, which had been observed at a neutral time, was strongly inhibited. Consequently, a local strong wind area was generated at the downstream of the terrain, and a strong wind area passing through the observation mast was observed. By investigating the increasing rate of speed of the local strong wind area induced at the time of stable stratification, it was found that the wind was approximately 1.2 times stronger than what was generated at a neutral time.
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Sardini, Nur Hidayat. „The Local Election Amidst the Oligarchs“. Humanities and Social Science Research 2, Nr. 1 (10.03.2019): p21. http://dx.doi.org/10.30560/hssr.v2n1p21.
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This article scrutinizes the phenomenon of Local Government Election (Local election) of a regency at the easternmost province in Indonesia, Jayapura Regency of Papua. During the election period, there was a great number of violations against election rules which were not only sporadic but also designed on a structured, systematic and massive scale – using the term of Indonesian Constitutional Courts. The violations were related to the role of the oligarchs who cooperatively worked hand in hand to win the political contestation. The activities of the oligarchs which involved clerical-technical issues are undoubtedly prohibited by the Law of Pilkada. The clerical-technical issues include unlawful activities such as replacing some officials of polling station a day before the election, manipulating the official report documents like voting and the calculation of the votes forms, certificates of results and holographic forms of the votes calculation details and records of the results of valid vote calculation at the polling stations in massive numbers. In the Jayapura Regency Election, it is found that the practice of the election administration regime is defied by an electoral shadow structure played by the Oligarchs. Thus, this article argues that the political decentralization results in a powerful control of the local oligarchs on the Local Elections which must be solved for the sake of Indonesia’s democratization.
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Vincent, Claire, Gregor Giebel, Pierre Pinson und Henrik Madsen. „Resolving Nonstationary Spectral Information in Wind Speed Time Series Using the Hilbert–Huang Transform“. Journal of Applied Meteorology and Climatology 49, Nr. 2 (01.02.2010): 253–67. http://dx.doi.org/10.1175/2009jamc2058.1.
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Abstract This work is motivated by the observation that large-amplitude wind fluctuations on temporal scales of 1–10 h present challenges for the power management of large offshore wind farms. Wind fluctuations on these scales are analyzed at a meteorological measurement mast in the Danish North Sea using a 4-yr time series of 10-min wind speed observations. An adaptive spectral analysis method called the Hilbert–Huang transform is chosen for the analysis, because the nonstationarity of time series of wind speed observations means that they are not well described by a global spectral analysis method such as the Fourier transform. The Hilbert–Huang transform is a local method based on a nonparametric and empirical decomposition of the data followed by calculation of instantaneous amplitudes and frequencies using the Hilbert transform. The Hilbert–Huang transformed 4-yr time series is averaged and summarized to show climatological patterns in the relationship between wind variability and time of day. First, by integrating the Hilbert spectrum along the frequency axis, a scalar time series representing the total variability within a given frequency range is calculated. Second, by calculating average spectra conditional to time of day, the time axis of the Hilbert spectrum is “remapped” to show climatological patterns. Third, the daily patterns in wind variability and wind speed are compared for the four seasons of the year. It is found that the most intense wind variability occurs in autumn even though the strongest observed wind speeds occur in winter.
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Nefedkin, S. I., A. O. Barsukov, M. I. Mozgova, M. S. Shichkov und M. A. Klimova. „Autonomous energy supply based on the wind-energy complex and hydrogen energy storage“. Alternative Energy and Ecology (ISJAEE), Nr. 16-18 (29.07.2019): 12–26. http://dx.doi.org/10.15518/isjaee.2019.16-18.12-26.
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The paper proposes an alternative scheme of guaranteed electricity and heat supply of an energy-insulated facility with a high potential of wind energy without the use of imported or local fuel. The scheme represents a wind power complex containing the park of wind generators located at the points with high wind potential. The wind generators provide guaranteed power supply even in periods of weak wind. For heat supply of the consumer, all surplus of the electric power goes on thermoelectric heating of water in tanks of accumulators, and also on receiving hydrogen by a method of electrolysis of water. The current heat supply is carried out with the use of hot water storage tanks, and the heat supply during the heat shortage is carried out by burning the stored hydrogen in condensing hydrogen boilers. We have developed the algorithm of calculation and the program "Wind in energy" which allows calculating annual balance of energy and picking up necessary quantity of the equipment for implementation of the scheme proceeding from the annual schedule of thermal and electric loading, and also potential of wind energy in the chosen region. The calculation-substantiation of the scheme proposed in relation to the real energy-insulated object Ust-Kamchatsk (Kamchatka) is carried out. The equipment for the implementation of an alternative energy supply scheme without the use of imported fuel is selected and compared with the traditional energy supply scheme based on a diesel power plant and a boiler house operating on imported fuel. With the introduction of an alternative power supply scheme, the equipment of the traditional scheme that has exhausted its resource can be used for backup power supply. Using climate databases, a number of energy-insulated facilities in the North and East of Russia with high wind energy potential are considered and the conditions for the successful implementation of the energy supply scheme are analyzed. This requires not only a high average annual wind speed, but also a minimum number of days of weak wind. In addition, it is necessary that the profile of the wind speed distribution in the annual section coincides with the profile of the heat load consumption.
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Zagubień, Adam, und Ryszard Ingielewicz. „The analysis of similarity of calculation results and local measurements of wind farm noise“. Measurement 106 (August 2017): 211–20. http://dx.doi.org/10.1016/j.measurement.2017.03.041.
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Villa Nova, Nilson A., Jarbas H. de Miranda, André B. Pereira und Késia O. da Silva. „Estimation of the potential evapotranspiration by a simplified penman method“. Engenharia Agrícola 26, Nr. 3 (Dezember 2006): 713–21. http://dx.doi.org/10.1590/s0100-69162006000300007.
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The numerous methods for calculating the potential or reference evapotranspiration (ETo or ETP) almost always do for a 24-hour period, including values of climatic parameters throughout the nocturnal period (daily averages). These results have a nil effect on transpiration, constituting the main evaporative demand process in cases of localized irrigation. The aim of the current manuscript was to come up with a model rather simplified for the calculation of diurnal daily ETo. It deals with an alternative approach based on the theoretical background of the Penman method without having to consider values of aerodynamic conductance of latent and sensible heat fluxes, as well as data of wind speed and relative humidity of the air. The comparison between the diurnal values of ETo measured in weighing lysimeters with elevated precision and estimated by either the Penman-Monteith method or the Simplified-Penman approach in study also points out a fairly consistent agreement among the potential demand calculation criteria. The Simplified-Penman approach was a feasible alternative to estimate ETo under the local meteorological conditions of two field trials. With the availability of the input data required, such a method could be employed in other climatic regions for scheduling irrigation.
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Wang, Hao, Shitang Ke, Yaojun Ge und Yukio Tamura. „Extreme and spectrum characteristics of wind loads on super-large cooling tower under different four-tower combinations“. Advances in Structural Engineering 22, Nr. 5 (09.11.2018): 1238–50. http://dx.doi.org/10.1177/1369433218810888.
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The wind loads distribution on the super-large cooling tower under the interference effect of tower group is very complicated. Particularly, energy distribution of fluctuation wind loads and extreme model is difficult to be predicted. However, accurate calculations of these two factors are the most direct ways for analysis of wind resistance dynamics of super-large cooling tower. The wind tunnel tests of the highest super-large cooling tower under five typical tower combinations (serial, rectangular, rhombus, L-shaped, and inclined L-shaped) with 320 working conditions were performed. On this basis, non-Gaussian and non-stationary properties of local wind pressure and overall force coefficient of super-large cooling tower were analyzed. Distribution laws of local wind pressure extremes and overall force coefficient extremes were discussed based on Hermite method and peak factor method. Key attention was paid to the mapping relationships of characteristic angles with local and overall aerodynamic force extremes. The effects of four-tower combination modes on fluctuation wind loads energy of super-large cooling tower were studied based on the power spectral density function, intrinsic mode function, and evolution power spectral density function. Besides, the estimation formulas of local wind pressure spectrum and overall pressure coefficient spectrum of super-large cooling tower under four-tower combination were proposed. It can be found that the extremes of local wind pressure and overall aerodynamic force could be predicted based on the linear relationship between characteristic angles and fluctuation wind loads. In addition, it is suggested to choose serial combination first, followed by inclined L-shaped, L-shaped, rhombus, and rectangular modes successively.
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Bi, Yao Zu, und Ben Thornber. „The Influence of Incoming Boundary Layer on the Flow around the Surface Excrescence“. Applied Mechanics and Materials 846 (Juli 2016): 48–53. http://dx.doi.org/10.4028/www.scientific.net/amm.846.48.
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This paper is concerned with the accurate prediction of parasitic drag due to excrescences introduced by structural repairs to aircraft wings and fuselage. Numerical computations are carried out to quantify the effect of isolated surface excrescences in a turbulent boundary layer on a flat plate. Both step excrescence in 2-D domain and wall-mounted hexahedron in 3-D domain are considered in the investigation. Various approaches for calculating drag coefficient increments for wing repair plates are presented. Menter's Shear Stress Transport (SST k-ω) turbulence model is employed here for its accurate prediction of aeronautics flows at typical repair locations with strong adverse pressure gradients and separation. Solutions are obtained via a high-order numerical scheme and an implicit time-marching approach on a multi-block structured mesh. A grid resolution study was carried out to confirm the accuracy of the computations. From the results curves are drawn showing the variation of parasitic drag components for a range of controlled speed (Mach 0.1 to 0.8), local Reynolds number (104 to 107) and the height of excrescence (y+=102 to 104).
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Wang, Ying Jun, Si Rong Zhu und Jian Jun Wang. „The Ply Optimum Design of Composites Wind Turbine Blade Based on the Local Stability“. Advanced Materials Research 988 (Juli 2014): 445–48. http://dx.doi.org/10.4028/www.scientific.net/amr.988.445.
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Fluid-solid coupling calculations are performed on design of a wind turbine blade made by fiber reinforced polymer composites. The length of the blade is 46m, and it is for a 3MW-capacity power station. By the finite element method, the initial design on the ply is carried out under the case of static loads. Then, the eigenvalue buckling theory is used to analyze the stability. In the process of design, sections of the blade which have different stiffness have different ply orientation and thickness. Thus, the local structural stiffness is enhanced, and the local stability of the blade is improved. The results show that the buckling load coefficient increases from 3.3 to 4.2, and the weight of the blade reduces by 4.5%. The aim of optimization design on the wind turbine blade has been achieved.
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van der Laan, Maarten Paul, Søren Juhl Andersen und Pierre-Elouan Réthoré. „Brief communication: Wind-speed-independent actuator disk control for faster annual energy production calculations of wind farms using computational fluid dynamics“. Wind Energy Science 4, Nr. 4 (02.12.2019): 645–51. http://dx.doi.org/10.5194/wes-4-645-2019.
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Abstract. A simple wind-speed-independent actuator disk control method is proposed that can be applied to speed up annual energy production calculations of wind farms using Reynolds-averaged Navier–Stokes simulations. The new control method allows the user to simulate the effect of different wind speeds in one simulation by scaling a calibrated thrust coefficient curve, while keeping the inflow constant. Since the global flow is not changed, only the local flow around the actuator disks need be recalculated from a previous converged result, which reduces the number of required iterations and computational effort by a factor of about 2–3.
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Prud’homme, Simon, Frederic Legeron und Sébastien Langlois. „Calculation of wind forces on lattice structures made of round bars by a local approach“. Engineering Structures 156 (Februar 2018): 548–55. http://dx.doi.org/10.1016/j.engstruct.2017.11.065.
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Alesbe, Israa, Moustafa Abdel-Maksoud und Sattar Aljabair. „Investigation of the Unsteady Flow Behaviour on a Wind Turbine Using a BEM and a RANSE Method“. Journal of Renewable Energy 2016 (2016): 1–12. http://dx.doi.org/10.1155/2016/6059741.
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Analyses of the unsteady flow behaviour of a 5 MW horizontal-axis wind turbine (HAWT) rotor (Case I) and a rotor with tower (Case II) are carried out using a panel method and a RANSE method. The panel method calculations are obtained by applying the in-house boundary element method (BEM) panMARE code, which is based on the potential flow theory. The BEM is a three-dimensional first-order panel method which can be used for investigating various steady and unsteady flow problems. Viscous flow simulations are carried out by using the RANSE solver ANSYS CFX 14.5. The results of Case I allow for the calculation of the global integral values of the torque and the thrust and include detailed information on the local flow field, such as the pressure distribution on the blade sections and the streamlines. The calculated pressure distribution by the BEM is compared with the corresponding values obtained by the RANSE solver. The tower geometry is considered in the simulation in Case II, so the unsteady forces due to the interaction between the tower and the rotor blades can be calculated. The application of viscous and inviscid flow methods to predict the forces on the HAWT allows for the evaluation of the viscous effects on the calculated HAWT flows.
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Yusran, Yusfan Adeputera, Sri Utami, Surjono und Atsar Yaisy Muhammad. „Ethnomodelling on atag construction in Ajung Village, Jember Regency“. ARTEKS : Jurnal Teknik Arsitektur 6, Nr. 1 (01.04.2021): 129–38. http://dx.doi.org/10.30822/arteks.v6i1.644.
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Atag functions as a place for the air curing process to dry tobacco leaves. This building, which is made of bamboo, has existed in Indonesia since 1850 and used to produce authentic quality cigars. Initially, this building was only utilized for local materials, however, based on the shape, dimensions, and construction, there is a tendency for atag to be established by considering several technical aspects. Therefore, this study aims to examine the technical ideas, such as calculations, practices, and procedures for making Atag using the ethnomodelling strategy. The results showed that the community's practices and calculations in building atag were a logical response in adapting to natural conditions such as climate, wind, and humidity. It also provided intelligence in utilizing the potential of local materials such as bamboo and sugarcane leaves
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Rogers, W. Erick, Alexander V. Babanin und David W. Wang. „Observation-Consistent Input and Whitecapping Dissipation in a Model for Wind-Generated Surface Waves: Description and Simple Calculations“. Journal of Atmospheric and Oceanic Technology 29, Nr. 9 (01.09.2012): 1329–46. http://dx.doi.org/10.1175/jtech-d-11-00092.1.
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Abstract A new wind-input and wind-breaking dissipation for phase-averaged spectral models of wind-generated surface waves is presented. Both are based on recent field observations in Lake George, New South Wales, Australia, at moderate-to-strong wind-wave conditions. The respective parameterizations are built on quantitative measurements and incorporate new observed physical features, which until very recently were missing in source terms employed in operational models. Two novel features of the wind-input source function are those that account for the effects of full airflow separation (and therefore relative reduction of the input at strong wind forcing) and for nonlinear behavior of this term. The breaking term also incorporates two new features evident from observational studies; the dissipation consists of two parts—a strictly local dissipation term and a cumulative term—and there is a threshold for wave breaking, below which no breaking occurs. Four variants of the dissipation term are selected for evaluation, with minimal calibration to each. These four models are evaluated using simple calculations herein. Results are generally favorable. Evaluation for more complex situations will be addressed in a forthcoming paper.
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Sahin, Ahmet Duran, und Zekai Sen. „Wind Energy Directional Spatial Correlation Functions and Application for Prediction“. Wind Engineering 24, Nr. 3 (Mai 2000): 223–31. http://dx.doi.org/10.1260/0309524001495576.
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In planning, design, operation and maintenance of wind farms, the spatial variations in wind velocity become significant. Although there are many wind energy studies at a single location, spatial assessment evaluation methods are scanty. Wind velocity maps may provide a common basis for regional assessment and interpretations, but they do not yield means of regional prediction. Hence, the main purpose of this paper is to propose some new concepts and methods that are useful prior to regional wind energy potential calculations. Among these are Directional Point Cumulative Semivariogram (DPCSV) concepts, which provide information concerning local spatial wind velocity and/or elevation changes. It is possible to obtain the radius of wind velocity influence around each station, along desired directions, based on the DPCSV concept. The implementation of the proposed methodology is presented for some wind velocity measurement stations in Turkey. For the application, the sample DPCSVs are first obtained from the available data, and then converted to Local Spatial Dependence Functions (LSDF). These functions are the basic ingredients for the regional wind velocity estimations. The reliability of the methodology is measured through the cross validation procedure and it is observed that the procedure is valid with less than 20% error.
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Møller, Mathias, Piotr Domagalski und Lars Roar Sætran. „Comparing abnormalities in onshore and offshore vertical wind profiles“. Wind Energy Science 5, Nr. 1 (30.03.2020): 391–411. http://dx.doi.org/10.5194/wes-5-391-2020.
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Abstract. Understanding the vertical wind profile is paramount for design and operation of wind turbines. It is needed not only for extrapolation of the wind velocity to hub height but also for structural load calculations, to name the most obvious issues. As wind turbines grow in size and development transitions offshore, issues such as shallow surface layers, low-level jets (LLJs) and internal boundary layers (IBLs) are raising questions concerning the applicability of the commonly used Monin–Obukhov similarity theory to accurately describe the vertical wind development at modern wind turbine hub heights. In this study the 10 min averaged vertical wind profile up to a minimum elevation of 100 m is analyzed through measurements collected from seven sites which represent a span of conditions. Three sites are located offshore in the North Sea and Baltic Sea (FINO1, FINO2 and FINO3) with varying fetch, two onshore by the Norwegian coast (Frøya and Valsneset), one further onshore by the Danish coast (Høvsøre), and one inland at a forested site in Sweden (Ryningsnäs). Through analysis of data series ranging from 8 months to several years depending on the site, the wind profile has been quantitatively categorized according to the number of exhibited local maxima which is not possible within the Monin–Obukhov similarity theory. The results reveal that the occurrence of local maxima is higher at sites of low surface roughness and a high prevalence of unstable atmospheric conditions, causing up to 17 % severely inflected abnormal profiles at the most exposed offshore site, which decreases as the location transitions from offshore to coastal to further inland and is lowest at the forested site. The results indicate that issues in predicting the vertical wind profile are most prevalent offshore, where very stable inflections cause severe deviations which may be related to an offshore internal boundary layer. These findings suggest that there is evident need of an improved vertical wind profile description in order to improve the accuracy of power predictions and load calculations, especially at offshore and coastal sites.
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Lopes, A. M. G., L. M. Ribeiro, D. X. Viegas und J. R. Raposo. „Effect of two-way coupling on the calculation of forest fire spread: model development“. International Journal of Wildland Fire 26, Nr. 9 (2017): 829. http://dx.doi.org/10.1071/wf16045.
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The present work addresses the problem of how wind should be taken into account in fire spread simulations. The study was based on the software system FireStation, which incorporates a surface fire spread model and a solver for the fluid flow (Navier–Stokes) equations. The standard procedure takes the wind field computed from a single simulation in the absence of fire, but this may not be the best option, especially for large fires. The two-way coupling method, however, considers the buoyancy effects caused by the fire heat release. Fire rate of spread is computed with the semi-empirical Rothermel model, which takes as input local terrain slope, fuels properties and wind speed and direction. Wind field is obtained by solving the mass, momentum and energy equations. Effects of turbulence on the mean flow field are taken into account with the k – ϵ turbulence model. The calculation procedure consists of an interchange between the fire spread model and the wind model through a dynamic interaction. The present work describes the first part of this research, presenting the underlying models and a qualitative sensitivity analysis. It is shown that the update frequency for the dynamic interaction markedly influences the total calculation time. The best strategy for updating the wind field during the fire progression is presented. The dependence of results on mesh size is also described.
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Mott, Rebecca, und Michael Lehning. „Meteorological Modeling of Very High-Resolution Wind Fields and Snow Deposition for Mountains“. Journal of Hydrometeorology 11, Nr. 4 (01.08.2010): 934–49. http://dx.doi.org/10.1175/2010jhm1216.1.
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Abstract The inhomogeneous snow distribution found in alpine terrain is the result of wind and precipitation interacting with the snow surface. During major snowfall events, preferential deposition of snow and transport of previously deposited snow often takes place simultaneously. Both processes, however, are driven by the local wind field, which is influenced by the local topography. In this study, the meteorological model Advanced Regional Prediction System (ARPS) was used to compute mean flow fields of 50-m, 25-m-, 10-m-, and 5-m grid spacing to investigate snow deposition patterns resulting from two snowfall events on a mountain ridge in the Swiss Alps. Only the initial adaptation of the flow field to the topography is calculated with artificial boundary conditions. The flow fields then drive the snow deposition and transport module of Alpine3D, a model of mountain surface processes. The authors compare the simulations with partly new measurements of snow deposition on the Gaudergrat ridge. On the basis of these four grid resolutions, it was possible to investigate the effects of numerical resolution in the calculation of wind fields and in the calculation of the associated snow deposition. The most realistic wind field and deposition patterns were obtained with the highest resolution of 5 m. These high-resolution simulations confirm the earlier hypothesis that preferential deposition is active at the ridge scale and true redistribution—mainly via saltation—forms smaller-scale deposition patterns, such as dunes and cornices.
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Duc, Thomas, Olivier Coupiac, Nicolas Girard, Gregor Giebel und Tuhfe Göçmen. „Local turbulence parameterization improves the Jensen wake model and its implementation for power optimization of an operating wind farm“. Wind Energy Science 4, Nr. 2 (22.05.2019): 287–302. http://dx.doi.org/10.5194/wes-4-287-2019.
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Abstract. In this paper, a new calculation procedure to improve the accuracy of the Jensen wake model for operating wind farms is proposed. In this procedure, the wake decay constant is updated locally at each wind turbine based on the turbulence intensity measurement provided by the nacelle anemometer. This procedure was tested against experimental data at the Sole du Moulin Vieux (SMV) onshore wind farm in France and the Horns Rev-I offshore wind farm in Denmark. Results indicate that the wake deficit at each wind turbine is described more accurately than when using the original model, reducing the error from 15 % to 20 % to approximately 5 %. Furthermore, this new model properly calibrated for the SMV wind farm is then used for coordinated control purposes. Assuming an axial induction control strategy, and following a model predictive approach, new power settings leading to an increased overall power production of the farm are derived. Power gains found are on the order of 2.5 % for a two-wind-turbine case with close spacing and 1 % to 1.5 % for a row of five wind turbines with a larger spacing. Finally, the uncertainty of the updated Jensen model is quantified considering the model inputs. When checked against the predicted power gain, the uncertainty of the model estimations is seen to be excessive, reaching approximately 4 %, which indicates the difficulty of field observations for such a gain. Nevertheless, the optimized settings are to be implemented during a field test campaign at SMV wind farm in the scope of the national project SMARTEOLE.
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Holley, Brian M., Sandor Becz und Lee S. Langston. „Measurement and Calculation of Turbine Cascade Endwall Pressure and Shear Stress“. Journal of Turbomachinery 128, Nr. 2 (01.02.2005): 232–39. http://dx.doi.org/10.1115/1.2137744.
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The complex three-dimensional fluid flow on the endwall in an axial flow turbine blade or vane passage has been extensively investigated and reported on in turbomachinery literature. The aerodynamic loss producing mechanisms associated with the endwall flow are still not fully understood or quantitatively predictable. To better quantify wall friction contributions to endwall aerodynamic loss, low Mach number wind tunnel measurement of skin friction coefficients have been made on one endwall of a large scale cascade of high pressure turbine airfoils, at engine operating Reynolds numbers. Concurrently, predictive calculations of the endwall flow shear stress have been made using a computational fluid dynamics (CFD) code. Use of the oil film interferometry skin friction technique is described and applied to the endwall, to measure local skin friction coefficients and shear stress directions on the endwall. These are correlated with previously reported measured local endwall pressure gradients. The experimental results are discussed and compared to the CFD calculations, to answer questions concerning endwall aerodynamic loss predictive ability.
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Malmgren-Hansen, A., P. Mortensen und Bo Møller. „Modelling of Oxygen Depletion in Coastal Waters“. Water Science and Technology 17, Nr. 6-7 (01.06.1985): 967–78. http://dx.doi.org/10.2166/wst.1985.0194.
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The relative importance of nutrient loadings and hydrographical and meteorological conditions for oxygen conditions in the Thisted Bredning, Denmark were evaluated by intensive survey and model calculations. The influence of wind speed on the vertical mixing in the unstratified shallow waters was quantified and tested in an oxygen model. The significance of oxygen consuming biological processes on the oxygen conditions were tested. By the use of a eutrophication model, the influence of local discharges of sewage on the size of the oxygen producing and oxygen consuming processes in the Thisted Bredning was calculated. Calculations showed that only a minor increase in rates of the oxygen consuming processes result in a drastic rise in the probability of oxygen depletion.
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Badger, Jake, Helmut Frank, Andrea N. Hahmann und Gregor Giebel. „Wind-Climate Estimation Based on Mesoscale and Microscale Modeling: Statistical–Dynamical Downscaling for Wind Energy Applications“. Journal of Applied Meteorology and Climatology 53, Nr. 8 (August 2014): 1901–19. http://dx.doi.org/10.1175/jamc-d-13-0147.1.
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AbstractThis paper demonstrates that a statistical–dynamical method can be used to accurately estimate the wind climate at a wind farm site. In particular, postprocessing of mesoscale model output allows an efficient calculation of the local wind climate required for wind resource estimation at a wind turbine site. The method is divided into two parts: 1) preprocessing, in which the configurations for the mesoscale model simulations are determined, and 2) postprocessing, in which the data from the mesoscale simulations are prepared for wind energy application. Results from idealized mesoscale modeling experiments for a challenging wind farm site in northern Spain are presented to support the preprocessing method. Comparisons of modeling results with measurements from the same wind farm site are presented to support the postprocessing method. The crucial element in postprocessing is the bridging of mesoscale modeling data to microscale modeling input data, via a so-called generalization method. With this method, very high-resolution wind resource mapping can be achieved.
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Aalen, Lovise, und Ragnhild Louise Muriaas. „Power calculations and political decentralisation in African post-conflict states“. International Political Science Review 38, Nr. 1 (09.07.2016): 56–69. http://dx.doi.org/10.1177/0192512115615704.
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Although many African governments introduced provisions for subnational elections in the early 1990s, there is variation in the extent to which these reforms were implemented and sustained. Our inductive analysis of three post-conflict cases – Angola, Ethiopia and South Africa – suggests that one factor explaining this variation is elite discontinuity when an insurgent group wins power in the aftermath of conflict. Systems of subnational elections adopted by new governments with an extensive social base derived from an insurgency, as in South Africa and Ethiopia, have proved relatively robust. By contrast, in Angola, where there was no change of executive power after the conflict ended, routinised subnational elections have not been implemented. The identified causal mechanism is that, for the new governments in the first two cases, subnational elections served as opportunities to mobilise party support and to consolidate control by sidelining local elites aligned with the previous regime.
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Banner, Michael L., und Jin-Bao Song. „On Determining the Onset and Strength of Breaking for Deep Water Waves. Part II: Influence of Wind Forcing and Surface Shear“. Journal of Physical Oceanography 32, Nr. 9 (01.09.2002): 2559–70. http://dx.doi.org/10.1175/1520-0485-32.9.2559.
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Abstract Part I of this study describes the authors' findings on a robust threshold variable that determines the onset of breaking for unforced, irrotational deep water waves and proposes a means of predicting the strength of breaking if the breaking threshold is exceeded. Those results were based on a numerical study of the unforced evolution of fully nonlinear, two-dimensional inviscid wave trains and highlight the fundamental role played by the nonlinear wave group dynamics. In Part II the scope of these calculations is extended to investigate the additional influence of wind forcing and background shear on the evolution to breaking. Using the methodology described in Part I, the present study focuses on the influence of wind forcing and vertical shear on long-term evolution toward breaking or recurrence of the maximum of the local energy density within a wave group. It investigates the behavior of a dimensionless local growth rate parameter that reflects the mean energy flux to the energy maximum in the wave group and provides a clearer physical interpretation of the evolution toward recurrence or breaking. Typically, the addition of the wind forcing and surface layer shear results in only small departures from the irrotational, unforced cases reported in Part I. This indicates that nonlinear hydrodynamic energy fluxes within wave groups still dominate the evolution to recurrence or breaking even in the presence of these other mechanisms. Further, the calculations confirm that the breaking threshold for this growth rate found for unforced irrotational wave groups in Part I is also applicable for cases with wind forcing and shear typical of open ocean conditions. Overall, this approach provides an earlier and more decisive indicator for the onset of breaking than previously proposed breaking thresholds and suggests a foundation for predicting the strength of breaking events.
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Friocourt, Yann, Bruno Blanke, Sybren Drijfhout und Sabrina Speich. „On the Dynamics of the Slope Current System along the West European Margin. Part II: Analytical Calculations and Numerical Simulations with Seasonal Forcing“. Journal of Physical Oceanography 38, Nr. 12 (01.12.2008): 2619–38. http://dx.doi.org/10.1175/2008jpo3745.1.
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Abstract The seasonality of the baroclinic slope current system along the western European margin in the Bay of Biscay and along the northern Iberian Peninsula is investigated in a joint analysis of an analytical model and numerical simulations with various forcings. A distinction is made between local winds and basin-scale winds, in which the effect of the latter is indirectly apparent through the basin-scale density gradients. The slope currents are mainly forced by the large-scale structure of the density field. The analysis indicates significant differences in the behavior of the uppermost slope current and of the deeper currents. At all depths, seasonal variations in the large-scale density structure of the ocean alter the strength of the slope currents but are not able to cause robust, long-lasting reversals. Reversals of the uppermost slope current appear to be caused by changes in the alongshore component of the local wind stress, provided that the opposing forcing from the density structure is weak enough. However, the deeper slope currents are not very much affected by the wind stress, so that flow reversals can be explained neither by the wind nor by seasonal changes in the density structure. A numerical simulation suggests that the reversals of the deeper slope currents are at least partly forced by seasonal changes in the flow upstream of the slope current system. The authors demonstrate that the larger part of these seasonal changes is associated with annual baroclinic Rossby waves caused by the seasonal cycle of the large-scale wind stress over the whole basin.
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Zheng, Hui Ping, Min Xue, Yu Han und Wen Chao Zhang. „Application of the Variation Coefficient Method to Comprehensive Evaluation of Wind Farms“. Applied Mechanics and Materials 488-489 (Januar 2014): 1447–53. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.1447.
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The wind resource has the intermittence characteristic, and the electricity quantity of a wind farm is determined by the local wind resource. In practice, it is difficult to compare the economic operation situations of wind farms in different conditions. Evaluation indicators of economic operation for wind farms are discussed according to actual operation and monitoring situations of wind farms. The high/low frequency ride through of wind farms, the low voltage ride through of wind turbines, the SVC/SVG dynamic response characteristics and the ability of active power control are used for evaluation on wind farms. Then through consistency processing, dimensionless processing and weight calculating, a comprehensive evaluation method based on the variation coefficient method and the distance integrated evaluation method is established. The effectiveness of the evaluation system is verified by comparison of three different wind farms. Finally, the operation conditions of all the wind farms are ranked by the obtained relative approach degrees.
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CUI, HAO-LEI, und HUI-SHEN SHEN. „MODELING AND SIMULATION OF BUCKLING AND POSTBUCKLING OF PLANT STEMS UNDER COMBINED LOADING CONDITIONS“. International Journal of Applied Mechanics 03, Nr. 01 (März 2011): 119–30. http://dx.doi.org/10.1142/s1758825111000907.
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Numerical simulations for local buckling and postbuckling behavior of plant stems are presented under two combined loading cases: (1) axial compression (caused by axial grains) combined with wind pressure; and (2) bending moment (caused by eccentric axial grains) combined with wind pressure. Based on its microstructure, a hollow plant stem is modeled as a stringer stiffened multiwalled shell. The material properties of the stem are assumed to be orthotropic. The nonlinear governing equations for buckling and postbuckling of plant stems are solved through arc-length method along with Newton–Raphson technique. The numerical calculations are carried out using the finite element package ABAQUS. The results show that the postbuckling equilibrium path is unstable for plant stems subjected to axial compression or bending combined with relatively low values of wind pressure. Large reduction in buckling load and in postbuckling strength can be found even if the applied wind pressure is relatively small, which results in the easy occurrence of stem lodging.
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Leupold, S., R. Schelenz und G. Jacobs. „Method to determine the local load cycles of a blade bearing using flexible multi-body simulation“. Forschung im Ingenieurwesen 85, Nr. 2 (31.03.2021): 211–18. http://dx.doi.org/10.1007/s10010-021-00457-y.
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AbstractConventional methods for designing rolling bearings against fatigue assume that a bearing ring is fully rotating and that the load is ideally distributed over the rolling elements. Blade bearings in wind turbines, are operated under oscillating motions and dynamic loads. The load distribution is strongly dependent on the stiffness of the bearing rings and the surrounding structural components. This has been shown in numerous studies using FEM simulations for static load cases. In this paper a method is presented that reduces the calculation effort of the deformation of the bearing rings, so that a flexible integration into an aeroelastic mbs model of a wind turbine is possible. Thereby an average accuracy of 6.5% between FEM and mbs could be achieved. The model allows the determination of time series of the global load distribution of each raceway. By data processing of the simulation results, the number of load cycles and the maximum contact pressure for individual segments of the raceways could be determined and their fatigue probability could be estimated using the linear damage hypothesis according to Palmgren-Miner.
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Song, Xu Ri, Lei Wang, Lin Ye, Yu Zou, Jie Xu und Cheng Long Dou. „Analysis of Short-Circuit Calculation in Microgrid with Wind/Solar Micro-Sources Based on IEC STANDARD 60909“. Advanced Materials Research 1008-1009 (August 2014): 155–59. http://dx.doi.org/10.4028/www.scientific.net/amr.1008-1009.155.
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Microgrid are LV or MV electric networks which utilize various distributed generators (DG) to serve local loads.In this paper an equivalent model of a hybrid system including wind power and solar power generating units has been built based on the mathematical models of wind turbine(WT) and photovoltaic(PV).Control strategies of the converters have been also developed. The short-circuit current and voltage levels of the microgrid have been calculated respectively based on the IEC 60909 standard corresponding to the occurrence of a three-phases short-circuit at the Point of the Common Coupling(PCC). Simulation results verified that the micro sources and microgrid built in this paper can simulate the actual system operation very well, and it can provide a simulation platform for further study of operation characteristics of system-integrated microgrid.
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Calderón-Vargas, Fátima, David Asmat-Campos und Anselmo Carretero-Gómez. „Sustainable Tourism and Renewable Energy: Binomial for Local Development in Cocachimba, Amazonas, Peru“. Sustainability 11, Nr. 18 (06.09.2019): 4891. http://dx.doi.org/10.3390/su11184891.
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This article addresses the relationship between sustainable tourism and the use of renewable energy sources. To this end, we evaluate the spatial–temporal tourist flow evolution as well as the wind/solar energy potential in Cocachimba, which is located in the Amazonas region of Peru. This is a place that has seen a considerable increase in tourist activity in the past decade. This is a result of its rich flora and fauna, but especially because of the presence of the Gocta waterfall, considered the third highest in the world. Currently, business initiatives associated with a variety of touristic services have been started. However, there is still a lack of infrastructure, which negatively impacts the tourists’ ability to stay overnight. In order to improve the resident-directed services quality and sustainable tourism, we propose the incorporation of sustainable lodging houses that are based, as previously described, on the usage of clean energy sources, which are harmless to the natural environment. To respond effectively to all this, a methodology based on the use of highly reliable sources and databases, statistical analysis, and highly supported physical calculations was used. The study shows that during the peak season there is insufficient lodging. Furthermore, by incorporating sustainable lodging houses, a reduction in fixed costs for the lodging establishments can be reached. We also found that the solar/wind potential possesses the minimal conditions necessary in order to implement heating systems and sustainable electrification based on conventional systems.
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Chang, Zhengping, Zhongqi Wang, Bo Jiang, Jinming Zhang, Feiyan Guo und Yonggang Kang. „Modeling and predicting of aeronautical thin-walled sheet metal parts riveting deformation“. Assembly Automation 36, Nr. 3 (01.08.2016): 295–307. http://dx.doi.org/10.1108/aa-10-2015-077.
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Purpose Riveting deformation is inevitable because of local relatively large material flows and typical compliant parts assembly, which affect the final product dimensional quality and fatigue durability. However, traditional approaches are concentrated on elastic assembly variation simulation and do not consider the impact of local plastic deformation. This paper aims to present a successive calculation model to study the riveting deformation where local deformation is taken into consideration. Design/methodology/approach Based on the material constitutive model and friction coefficient obtained by experiments, an accurate three-dimensional finite element model was built primarily using ABAQUS and was verified by experiments. A successive calculation model of predicting riveting deformation was implemented by the Python and Matlab and was solved by the ABAQUS. Finally, three configuration experiments were conducted to evaluate the effectiveness of the model. Findings The model predicting results, obtained from two simple coupons and a wing panel, showed that it was a good compliant with the experimental results, and the riveting sequences had a significant effect on the distribution and magnitude of deformation. Practical implications The proposed model of predicting the deformation from riveting process was available in the early design stages, and some efficient suggestions for controlling deformation could be obtained. Originality/value A new predicting model of thin-walled sheet metal parts riveting deformation was presented to help the engineers to predict and control the assembly deformation more exactly.
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Abdou, Wed Abdellatif Ibrahim. „A New Approach to Assessment of Bird Carcass Removal (Scavenging) Time on Wind Farm in Egypt“. Ring 41, Nr. 1 (01.12.2019): 17–25. http://dx.doi.org/10.1515/ring-2019-0002.
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Abstract Wind farms developing rapidly in order to meet the high demand for energy from green sources. However, the impact of wind farm operation on the environment still needs to be established. The risk to wild birds is drawing the attention of stakeholders and bird conservation organizations. Carcass search is the main method used to assess the impact of wind farm operation on wild birds of various systematic groups and sizes. Assessment of the overall risk that wind farms pose to birds depends primarily on accurate calculation of carcass removal times and the detection ability of the searcher. Most studies have assessed the carcass removal time using pet bird species, pigeons, or various local birds. In Egypt, all studies conducted in operating wind farms up to 2016 had used chickens to assess the carcass removal time and in this way to the estimate the total number of bird fatalities within wind farms. The use of birds killed by a wind farm in carcass removal trials provides the actual time of carcass disappearance, in contrast with the use of other bird species. The removal times of carcasses of parakeets, quails, partridges and chickens were shorter than those of carcasses of White Stork, White Pelican, Honey Buzzard, Black Kites and eagles used in the current study and in another study in Australia. The results of the present study indicate that carcasses of birds killed within the studied wind farm remain for two to three months, while the carcasses of other in species other localities remain no more than 1 to 15 days, which unquestionably influences the calculation of total fatalities and leads to overestimation of the overall risk that wind farms for birds.