Academic literature on the topic 'Aerodynamický paket'
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Journal articles on the topic "Aerodynamický paket"
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Cao, Jian, Cen Rui Ma, and Xiao Jiang Hu. "Improving Performance of Wireless-Optical Broadband Access Network by Interpolation Algorithm of Zadoff-Chu Sequence." Advanced Materials Research 989-994 (July 2014): 2495–98. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.2495.
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HF channel sounding requires perfect autocorrelation property of the sounding sequences. Compared with other pseudonoise sounding sequences, Zadoff-Chu sequence gets great attention due to its predominant periodic autocorrelation property. A Wireless-Optical Broadband Access Network (WOBAN) is gaining more attention because its good performance and merits such as reliability, robustness and high capacity as well as flexibility. There are many factors that can affect the network performance, such as delay, packet loss and capacity utilization. Application examples show that, this system can significantly improve the efficiency of aerodynamic design.
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Cao, Jian, Hai Ying Ma, and Gang Li. "Research on a New Type of Multi-Link Variable Compression Ratio by Interpolation Algorithm of Zadoff-Chu Sequence." Applied Mechanics and Materials 602-605 (August 2014): 3392–95. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.3392.
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Compared with the traditional multi-link and variable compression ratio mechanism, the new engine had compact styling and lower designed costs. There are many factors that can affect the engine network performance, such as delay, packet loss and capacity utilization. Application examples show that, this system can significantly improve the efficiency of aerodynamic design. Compare the kinematics function with the new design with the prototype 250 engine and the traditional multi-link and variable compression ratio mechanism by using the virtual simulation software MSC-Adams. The contrast result suggested that the new design had higher combustion efficiency and charging efficiency than the prototype engine.
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Yevseiev, Serhii, Oleksandr Kuznietsov, Sergey Herasimov, Stanislav Horielyshev, Anton Karlov, Ihor Kovalov, Oleksii Kolomiitsev, Olena Lukashuk, Oleksandr Milov, and Vitaliy Panchenko. "Development of an optimization method for measuring the Doppler frequency of a packet taking into account the fluctuations of the initial phases of its radio pulses." Eastern-European Journal of Enterprise Technologies 2, no. 9 (110) (April 30, 2021): 6–15. http://dx.doi.org/10.15587/1729-4061.2021.229221.
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The necessity of estimating the decrease in the accuracy of measuring the informative parameters of a radar signal in real conditions of its propagation and reflection has been substantiated. The results of the estimation determine the requirements for optimizing this measurement to achieve the required efficiency. A numerical analysis of the decrease in the accuracy of measuring the Doppler frequency of a coherent packet is presented, depending on the statistical characteristics of fluctuations of the initial phases of its radio pulses. Expressions are given for calculating the fluctuation component of the measurement error of radio pulse packet frequency for various coefficients of interpulse correlation of phase fluctuations. An assessment is made of the possibility of increasing the accuracy of Doppler frequency measurement, which can be ensured by statistical optimization of the algorithm for time-frequency processing of a given radar signal by taking into account its phase fluctuations. The conditions for the multiplicative influence of phase fluctuations of radio pulses of the received packet are substantiated, which determine the efficiency of optimization of Doppler frequency measurement. Based on the results of the study, an optimization method for measuring the Doppler frequency of the packet taking into account fluctuations in the initial phases of its radio pulses is proposed. The accuracy of Doppler frequency measurement under the influence of both the internal noise of the radar receiver and the correlated phase fluctuations of its radio pulses is estimated. The efficiency of optimization of measuring the Doppler frequency of the packet is estimated taking into account fluctuations of the initial phases of its radio pulses by means of computer simulation. It is proved that, under the influence of phase fluctuations, the accuracy of Doppler frequency measurement can be increased due to the performed optimization from 1.86 to 6.29 times. This opens the way to improving the existing algorithms for measuring the higher time range derivatives to improve the quality of tracking complex maneuvering aerodynamic objects. This explains the importance and usefulness of the work for the radar theory.
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Indrusiak, M. L. S., A. J. Kozakevicius, and S. V. Möller. "WAVELET ANALYSIS CONSIDERATIONS FOR EXPERIMENTAL NONSTATIONARY FLOW PHENOMENA." Revista de Engenharia Térmica 15, no. 1 (June 30, 2016): 67. http://dx.doi.org/10.5380/reterm.v15i1.62149.
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In this work, wavelet transforms are the analysis tools for studying transient and discontinuous phenomena associated to turbulent flows. The application in quest results from velocity measurements with hot wire anemometry in the transient wake considering a circular cylinder in an aerodynamic channel. Continuous and discrete wavelet transforms are applied and compared with the corresponding results given by the Fourier transform. For the continuous wavelet transform, the Morlet function was adopted as transform basis, and for the discrete case, the Daubechies orthonormal wavelet with 20 null moments. Results using the discrete wavelet packet transform are also presented and compared. A wake past a cylinder was analytically simulated and compared with the actual one, both in transient flow. The ability of the wavelet transforms in the analysis of unsteady phenomena and the potential of the wavelet approach as a complementary tool to the Fourier spectrum for the analysis of stationary phenomena is presented and discussed.
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Chen, Xi, Fotis Kopsaftopoulos, Qi Wu, He Ren, and Fu-Kuo Chang. "A Self-Adaptive 1D Convolutional Neural Network for Flight-State Identification." Sensors 19, no. 2 (January 11, 2019): 275. http://dx.doi.org/10.3390/s19020275.
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The vibration of a wing structure in the air reflects coupled aerodynamic–mechanical responses under varying flight states that are defined by the angle of attack and airspeed. It is of great challenge to identify the flight state from the complex vibration signals. In this paper, a novel one-dimension convolutional neural network (CNN) is developed, which is able to automatically extract useful features from the structural vibration of a recently fabricated self-sensing wing through wind-tunnel experiments. The obtained signals are firstly decomposed into various subsignals with different frequency bands via dual-tree complex-wavelet packet transformation. Then, the reconstructed subsignals are selected to form the best combination for multichannel inputs of the CNN. A swarm-based evolutionary algorithm called grey-wolf optimizer is utilized to optimize a set of key parameters of the CNN, which saves considerable human efforts. Two case studies demonstrate the high identification accuracy and robustness of the proposed method over standard deep-learning methods in flight-state identification, thus providing new perspectives in self-awareness toward the next generation of intelligent air vehicles.
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Ливеринова, М. А., and Н. В. Тряскин. "Numerical determination of aerodynamic characteristics of an airfoil in a ground effect." MORSKIE INTELLEKTUAL`NYE TEHNOLOGII), no. 1(51) (March 5, 2021): 44–50. http://dx.doi.org/10.37220/mit.2021.51.1.024.
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В работе изучается движение профиля над экраном на различных относительных высотах. Рассмотрены следующие методы его моделирования: условие неподвижного экрана и метод зеркального отображения для моделирования обращённого движения и условие экрана, движущегося со скоростью профиля, что моделирует прямое движение. Целью работы является выбор метода моделирования экрана, при котором обтекание профиля соответствует действительности и оценка разницы между рассмотренными методами. Задача решена в открытом пакете OpenFOAM методом контрольного объёма, где совместно решены уравнения Навье-Стокса и неразрывности, осреднённые по Рейнольдсу. Произведена верификация и валидация математической модели и найдено сеточно-независимое решение. Выбраны два профиля в плане: сегментный и симметричный. Рассмотрены несколько относительных высот. В работе построены эпюры скоростей под профилем, представлены картины обтекания профилей, исследованы их основные эксплуатационные характеристики: коэффициент подъёмной силы и коэффициент сопротивления в зависимости от относительной высоты. Построено распределение коэффициента давления по поверхности рассматриваемых профилей в зависимости от граничных условий и относительных высот. В результате анализа показано различие происходящих физических процессов при обтекании профилей в прямом и обращённом движении. Данная работа позволяет сделать вывод о том, каким образом проводить физический эксперимент для различных профилей, показывает преимущество использования метода зеркальных отображений или подвижного экрана при проведении эксперимента. In this article the movement of the profile above the screen at different relative heights is reviewed. The following methods of its modeling are considered: the condition of a stationary screen and the method of images for simulating reverse motion and the condition of a screen moving with the profile speed that simulate forward motion are considered. The aim of the work is to select a screen simulation method for a physical experiment. An open-source packet OpenFOAM based on finite-volume method is used to solve the Navier-Stokes and continuity equations averaged by Reynolds method. The mathematical model is verified and validated, and a grid-independent solution is found. Two profiles are selected: segmental and symmetrical. Several relative heights are considered. The velocitiy profiles under the airfoil are constructed, the patterns of the flow around the airfoils are presented. The dependences of coefficients on the studied parameters and the distribution of the pressure coefficient over the profile are studied and analyzed. As a result of the analysis, the difference between the physical processes when flowing around the airfoils is in forward and reverse motion is shown. This work allows us to make a conclusion about how to conduct a model experiment for various profiles, shows the advantage of using the method of images or a movable screen in the experiment.
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Jalbi, Saleh, Joseph Hilton, and Luke Jacques. "Assessment of Practical Methods to Predict Accumulated Rotations of Monopile-Supported Offshore Wind Turbines in Cohesionless Ground Profiles." Energies 13, no. 15 (July 31, 2020): 3915. http://dx.doi.org/10.3390/en13153915.
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Monopiles supporting offshore wind turbines can experience permanent non-recoverable rotations (or displacements) during their lifetime due to the cyclic nature of hydrodynamic and aerodynamic loading exerted on them. Recent studies in the literature have demonstrated that conventional cyclic p–y curves recommended in different codes of practice (API-RP-2GEO and DNVGL-RP-C212) may not capture the effects of long-term cyclic loads as they are independent of the loading profile and the number of applied cycles. Several published methodologies based on laboratory scaled model tests (on sands) exist to determine the effect of cyclic lateral loads on the long-term behaviour of piles. The tests vary in terms of the pile behaviour (rigid or flexible pile), number of applied loading cycles, and the load profile (one-way or two-way loading). The best-fit curves provided by these tests offer practical and cost-efficient methods to quantify the accumulated rotations when compared to Finite Element Method. It is therefore desirable that such methods are further developed to take into account different soil types and the complex nature of the loading. The objective of this paper is to compare the performance of the available formulations under the actions of a typical 35-h (hour) storm as per the Bundesamt für Seeschifffahrt und Hydrographie (BSH) recommendations. Using classical rain flow counting, the loading time-history is discretized into load packets where each packet has a loading profile and number of cycles, which then enables the computation of an equivalent number of cycles of the largest load packet. The results show that the loading profile plays a detrimental role in the result of the accumulated rotation. Furthermore, flexibility of the pile also has an important effect on the response of the pile where predictions obtained from formulations based on flexible piles resulted in a much lower accumulated rotation than tests based on rigid piles. Finally, the findings of this paper are expected to contribute in the design and interpretation of future experimental frameworks for Offshore Wind Turbine (OWT) monopiles in sands, which will include a more realistic loading profile, number of cycles, and relative soil to pile stiffness.
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Wu, Xuesong, and Zhongyu Zhang. "First-principle description of acoustic radiation of shear flows." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2159 (October 14, 2019): 20190077. http://dx.doi.org/10.1098/rsta.2019.0077.
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As a methodology complementary to acoustic analogy, the asymptotic approach to aeroacoustics seeks to predict aerodynamical noise on the basis of first principles by probing into the physical processes of acoustic radiation. The present paper highlights the principal ideas and recent developments of this approach, which have shed light on some of the fundamental issues in sound generation in shear flows. The theoretical work on sound wave emission by nonlinearly modulated wavepackets of supersonic and subsonic instability modes in free shear flows identifies the respective physical sources or emitters. A wavepacket of supersonic modes is itself an efficient emitter, radiating directly intensive sound in the form of a Mach wave beam, the frequencies of which are in the same band as those of the modes in the packet. By contrast, a wavepacket of subsonic modes radiates very weak sound directly. However, the nonlinear self-interaction of such a wavepacket generates a slowly modulated mean-flow distortion, which then emits sound waves with low frequencies and long wavelengths on the scale of the wavepacket envelope. In both cases, the acoustic waves emitted to the far field are explicitly expressed in terms of the amplitude function of the wavepacket. The asymptotic approach has also been applied to analyse generation of sound waves in wall-bounded shear flows on the triple-deck scale. Several subtleties have been found. The near-field approximation has to be worked out to a sufficiently higher order in order just to calculate the far-field sound at leading order. The back action of the radiated sound on the flow in the viscous sublayer and the main shear layer is accounted for by an impedance coefficient. This effect is of higher order in the subsonic regime, but becomes a leading order in the transonic and supersonic regimes. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.
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Frihdianto, Fajar, Nyeyep Sri Wardani, and Indah Widiastuti. "ANALYSIS OF THE USE OF SPOILER ONE LEVEL AND TWO LEVELS IN CONDITIONS OF STEADY AGAINST THE DRAG AND LIFT COEFFICIENTS ON A SEDAN TYPE CAR BY USING CFD (COMPUTATIONAL FLUID DYNAMIC)." Journal of Mechanical Engineering and Vocational Education (JoMEVE) 1, no. 2 (April 2, 2019): 58. http://dx.doi.org/10.20961/jomeve.v1i2.25066.
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<p><em>This research was simulation analyzing the condition of steady flow in around of body car made and analized computly using CFD program (Computational Fluid Dynamic). The model used was Sedan car designed with different rear end body by adding spoiler. Analyzing in this research was done by using Software 18.2–CFD Student Version. Design of the three models were compared to find out the difference in magnitude of Coefficient of Drag, Coefficient of Lift, pressure distribution, velocity distribution, and behavioral character of flow around the rear end of car in the condition of steady flow. Model was made in appropriate scale with model of Honda city 2008 sedan car</em><em>. </em><em>Observation was made to look at the behavior of fluida flows both in front and back the car in different fluid speed ranges in steady condition.</em></p><p><em>The simulation results obtained from packet CFD on each condition were; model without spoiler, model with 1 level spoiler, and model with 2 level spoiler. Where this simulation showed that CD and CL were decrease</em><em>. </em><em>One of the example was at speed 40km/hour obtained the coefficient of drag (CD) of 0.31061, 0.28603, and 0.2054, it proved that 1 level spoiler could reduce the value of drag coefficient about 7.9135% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of drag coefficient about 33.8592% without spoiler. For the coefficient of lift (CL) on each model was -0.38487, -0.54624, and -0.62097 proved that spoiler 1 level could reduce the value of lift coeffient about 41.92845% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of lift coefficient about 61.35984% without spoiler. On the result of pressure distrubution and relative velocity give little affect to the upper and lower surface where this was indicated by almost no color difference contours. Then, if it was indicated from streamline and the formation of vortex, there was a significant difference so that it was very influential on the size of CD and CL occoured. By changing geometric proved that the spoiler car 1 and 2 level were more aerodynamic than the car without spoiler.</em></p>
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Corral, Roque, Juan Manuel Gallardo, and Carlos Martel. "A Conceptual Flutter Analysis of a Packet of Vanes Using a Mass-Spring Model." Journal of Turbomachinery 131, no. 2 (January 29, 2009). http://dx.doi.org/10.1115/1.2952364.
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The linear aeroelastic stability of a simplified mass-spring model representing the basic dynamics of a packet of Na airfoils has been used to uncover a new type of coupled mode flutter. This simple model retains an essential dynamical feature of the vane packet: the presence of a cluster of Na−1 nearly identical purely structural natural frequencies due to the much larger stiffness of the lower platform as compared to that of the airfoil. Using this model it may be seen that this degeneracy makes the Na−1 associated mode shapes extremely sensible to the addition of small perturbations such as the aerodynamic forces. Since the determination of the aerodynamic vibrational correction (damping and frequency) requires knowing the mode shape, the aerodynamic corrections of the Na−1 cluster modes are now unavoidably coupled together. Moreover, the computation of the aerodynamic correction independently for each structural mode shape leads typically to dangerously overpredicting the stabilizing effect of vane packing. It is shown that the expected stabilizing effect due to the packets may be negligible, depending on the relative frequency split associated with the strength of the aerodynamic forces and realistic structural effects such as the finite stiffness of the lower platform. It is also shown that in these cases, the most unstable mode may be, in a first approximation, very similar to that obtained modeling the stator as a continuous ring.
Dissertations / Theses on the topic "Aerodynamický paket"
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Malík, Jiří. "Design kapotáže studentské formule." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231733.
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Diplomová práce pojednává o návrhu kapotáže vozidla Formula Student. Vozy této kategorie se každoročně učástní série mezinárodních závodů všech zůčastněných studentských týmů. Úroveň návrhu se posuzuje jak v dynamických tak ve statických disciplínách. Tato práce popisuje proces návrhu tří koncepčních variant společně s rozpracováním finální varianty pro fázi výroby. Navíc je zde prezentován koncept obsahující aerodynamický paket, který slouží jako výhledová studie možného vývoje vozidla.
Conference papers on the topic "Aerodynamický paket"
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Corral, Roque, Juan Manuel Gallardo, and Carlos Martel. "A Conceptual Flutter Analysis of a Packet of Vanes Using a Mass-Spring Model." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27090.
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The linear aeroelastic stability of a simplified mass-spring model representing the basic dynamics of a sector of Na airfoils is analyzed. The degree of multiplicity of the eigenvalues of the simplified structural model is Na−1 and hence its mode-shapes are not determined in a unique way. The aerodynamic damping strongly depends on the mode shape and hence its accurate determination is essential in order to obtain realistic values of damping. This in-determination is removed when the aerodynamic forces associated to the motion of the airfoils are added or a platform with finite stiffness is considered. In both cases the problem is not degenerated anymore and the mode-shapes of the system are uniquely determined. It is shown that the expected stabilizing effect due to the packets may be negligible, depending on the relative strength of the aerodynamic forces and the stiffness of the lower platform. It is also shown that, for the most unstable situation, the aeroelastic behaviour of the problem may be, in first approximation, very similar to that of a continuous ring.
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MENGLE, V. "Packet flutter and aerodynamic modes for non-homogenous airfoil cascades in highly distorted, periodic, stationary throughflows." In 27th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-848.
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Misek, Tomas, Antonin Tetiva, Lubos Prchlik, and Karel Duchek. "Prediction of High Cycle Fatigue Life of Steam Turbine Blading Based on Unsteady CFD and FEM Forced Response Calculation." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27877.
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This paper presents the high cycle fatigue life prediction of a shrouded packet blade row for a large high pressure steam turbine. The fatigue life assessment was based on a loosely coupled CFD and FEM calculations supported by the direct cyclic mechanical testing of a full scale model of the blade root attachment. In the first stage, potentially dangerous vibration modes were identified from the linear finite element analyses and verified by testing. Aerodynamic forces acting on rotating blades were obtained from an unsteady sliding mesh CFD calculation based on a viscous unsteady compressible turbulent flow. A forced vibration analysis was then performed for critical resonance frequencies close to nozzle passing frequency considering only the inherent material damping. The calculated alternating stress in the blade root attachment was used to estimate the safety against the high cycle fatigue failure. Fatigue life was evaluated for current and new design of stationary vanes. In the new design the number of vanes was increased and their full 3D shape was optimized. Both changes reduced the excitation forces by more then an order of magnitude. The final evaluation showed that the vibratory stresses for the new design were well below the actual fatigue limit of the blade root attachment.