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Academic literature on the topic 'Multiharmonic analysi'

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Published: 10 March 2023

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Journal articles on the topic "Multiharmonic analysi"

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Langer, Ulrich, Sergey Repin, and Monika Wolfmayr. "Functional A Posteriori Error Estimates for Parabolic Time-Periodic Boundary Value Problems." Computational Methods in Applied Mathematics 15, no. 3 (July 1, 2015): 353–72. http://dx.doi.org/10.1515/cmam-2015-0012.

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AbstractThe paper is concerned with parabolic time-periodic boundary value problems which are of theoretical interest and arise in different practical applications. The multiharmonic finite element method is well adapted to this class of parabolic problems. We study properties of multiharmonic approximations and derive guaranteed and fully computable bounds of approximation errors. For this purpose, we use the functional a posteriori error estimation techniques earlier introduced by S. Repin. Numerical tests confirm the efficiency of the a posteriori error bounds derived.
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Kudashkina, L. S., and I. L. Andronov. "Multiharmonic analysis of Mira-type stars." Symposium - International Astronomical Union 180 (1997): 353. http://dx.doi.org/10.1017/s0074180900131286.

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The shapes of light curves of Mira-type variable stars are analyzed by using the multi–harmonic fit (Andronov 1994). The light curves of 63 stars best covered by the AAVSO observations and published by Mattei (1978) were used. Some correlations between the characteristics of the mean light curves were found.
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Deng, Yinbin, and Lingyu Jin. "Exponential decay of the solutions for nonlinear multiharmonic equations." Nonlinear Analysis: Theory, Methods & Applications 69, no. 7 (October 2008): 1953–65. http://dx.doi.org/10.1016/j.na.2007.07.036.

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Andronov, I. L. "Some new methods of time series analysis: Applications to the AGB stars." Symposium - International Astronomical Union 180 (1997): 341. http://dx.doi.org/10.1017/s0074180900131183.

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Some supplementary methods of time series analysis are described which are used for study of periodic and aperiodic variability of the AGB stars. These are “multiharmonic fits” used to fit the periodic (asinusoidal) curve; running approximations – “parabolae”, “sines”; “asymptotic parabolae”; “linear fits”.
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Cardona, Alberto, Thierry Coune, Albert Lerusse, and Michel Geradin. "A multiharmonic method for non-linear vibration analysis." International Journal for Numerical Methods in Engineering 37, no. 9 (May 15, 1994): 1593–608. http://dx.doi.org/10.1002/nme.1620370911.

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Bachinger, F., U. Langer, and J. Schöberl. "Numerical analysis of nonlinear multiharmonic eddy current problems." Numerische Mathematik 100, no. 4 (May 3, 2005): 593–616. http://dx.doi.org/10.1007/s00211-005-0597-2.

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Petrov, E. P. "A Method for Use of Cyclic Symmetry Properties in Analysis of Nonlinear Multiharmonic Vibrations of Bladed Disks." Journal of Turbomachinery 126, no. 1 (January 1, 2004): 175–83. http://dx.doi.org/10.1115/1.1644558.

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An effective method for analysis of periodic forced response of nonlinear cyclically symmetric structures has been developed. The method allows multiharmonic forced response to be calculated for a whole bladed disk using a periodic sector model without any loss of accuracy in calculations and modeling. A rigorous proof of the validity of the reduction of the whole nonlinear structure to a sector is provided. Types of bladed disk forcing for which the method may be applied are formulated. A multiharmonic formulation and a solution technique for equations of motion have been derived for two cases of description for a linear part of the bladed disk model: (i) using sector finite element matrices and (ii) using sector mode shapes and frequencies. Calculations validating the developed method and a numerical investigation of a realistic high-pressure turbine bladed disk with shrouds have demonstrated the high efficiency of the method.
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Kolmbauer, Michael, and Ulrich Langer. "A Robust Preconditioned MinRes Solver for Time-periodic Eddy Current Problems." Computational Methods in Applied Mathematics 13, no. 1 (January 1, 2013): 1–20. http://dx.doi.org/10.2478/cmam-2012-0023.

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Abstract.This work is devoted to fast and parameter-robust iterative solvers for frequency domain finite element equations, approximating the time-periodic eddy current problem with multiharmonic or time-periodic excitations in time. We construct a preconditioned MinRes solver for the frequency domain equations, that is robust with respect to the discretization parameters as well as all involved “bad” parameters like the conductivity, the reluctivity and possible regularization parameters.
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Berthillier, M., C. Dupont, R. Mondal, and J. J. Barrau. "Blades Forced Response Analysis With Friction Dampers." Journal of Vibration and Acoustics 120, no. 2 (April 1, 1998): 468–74. http://dx.doi.org/10.1115/1.2893853.

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A multiharmonic frequency domain analysis combined with a Craig-Bampton component mode synthesis is presented to compute the dry friction damped forced response of blades. The accuracy of the analysis is established, for a cantilever beam with a dry friction damper attached, by comparison with experimental results and time domain analysis. The method has then been applied to a model fan blade damped by a blade to ground damper.
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Chen, Jingfeng, Wenzhi Wang, Chong He, Yajun Li, Xianling Liang, Junping Geng, and Ronghong Jin. "Direction Finding Based on Time-Modulated Array With Multiharmonic Analysis." IEEE Transactions on Antennas and Propagation 68, no. 7 (July 2020): 5753–58. http://dx.doi.org/10.1109/tap.2020.2969972.

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Dissertations / Theses on the topic "Multiharmonic analysi"

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NTIBARIKURE, LAURENT. "Contributions to the Art of Finite Element Analysis in Electromagnetics." Doctoral thesis, 2014. http://hdl.handle.net/2158/843133.

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The finite element method is a powerful method for the approximate solution of boundary value problems governed by partial differential equations. A really first application to structural engineering problems, dating 1943, is attributed to R. Courant. Since then, there has been a lot of successful tentatives to apply the method to other fields. In particular, Silvester showed in 1969 that waveguide modes could be easily computed with the method. His work started a long path for finite elements in electromagnetics, with multiple assessments of the method with real-world problems and gradually improving the efficiency of the algorithms. Nowadays, finite elements in computational electromagnetics has become an invaluable part in radio frequency and microwave application designs, and many packages are widely available to perform these tasks. However, there remain a lot of problems to be solved. In this dissertation, we have inquired in two of these. The first, the efficient solution of large problems which may not be solvable on a single modern computer. Domain decomposition methods have been thus investigated, these allowing to solve smaller parts of a large problem and to achieve the whole solution upon proper interconnection. Two types of domain decomposition methods have been analyzed, leading to the construction of algorithms for solving large electromagnetic problems at a nearly linear complexity. The other, the accurate solution of electromagnetic problems in which some materials behave nonlinearly, that is their properties vary depending on the intensity of the fields they imbue. Almost all materials behave nonlinearly and their effect is just a matter of fields intensities and accuracy requirements. In many microwave applications, the nonlinear effects, necessary for information processing and control, are still limited to lumped devices for their highly developed models. Accurate modeling of bulk or films of nonlinear materials may open the way to a new variety of controllable materials in flexible, reconfigurable, electromagnetic devices. A finite element package has been implemented to perform several tests here documented.
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Book chapters on the topic "Multiharmonic analysi"

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Kudashkina, L. S., and I. L. Andronov. "Multiharmonic Analysis of MIRA-Type Stars." In Planetary Nebulae, 353. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5244-0_164.

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Conference papers on the topic "Multiharmonic analysi"

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Kong, M. G. "Energy spread analysis for a multiharmonic optical klystron (MHOK)." In 25th Anniversary, IEEE Conference Record - Abstracts. 1998 IEEE International Conference on Plasma Science (Cat. No.98CH36221). IEEE, 1998. http://dx.doi.org/10.1109/plasma.1998.677679.

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Petrov, E. P. "Analytical Formulation of Friction Contact Elements for Frequency-Domain Analysis of Nonlinear Vibrations of Structures With High-Energy Rubs." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90628.

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Abstract In gas-turbine engines and other rotating machinery structures rubbing contact interactions can occur when the contacting components have large relative motion between components: such as in rotating bladed disc-casing rubbing contacts, rubbing in rotor bearing and labyrinth seals, etc. The analysis of vibrations of structures with rubbing contacts requires the development of a mathematical model and special friction contact elements that would allow for the prescribed relative motion of rubbing surfaces in addition to the motion due to vibrations of the contacting components. In the proposed paper, the formulation of the friction contact elements is developed which includes the effects of the prescribed relative motion on the friction stick-slip transitions and, therefore, on the contact interaction forces. For a first time, the formulation is made for the frequency domain analysis of coupled rubbing and vibrational motion, using the multiharmonic representation of the vibration displacements. The formulation is made fully analytically to express the multiharmonic contact interaction forces and multiharmonic tangent stiffness matrix in an explicit analytical form allowing their calculation accurately and fast. The dependency of the friction and contact stiffness coefficients on the energy dissipated during high-energy rubbing contacts and, hence, on the corresponding increase of the contact interface temperature is included in the formulation. The efficiency of the developed friction elements is demonstrated on a set of test cases including simple models and a large-scale realistic blade.
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Petrov, E. P. "A Method for Use of Cyclic Symmetry Properties in Analysis of Nonlinear Multiharmonic Vibrations of Bladed Discs." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38480.

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An effective method for analysis of periodic forced response of nonlinear cyclically symmetric structures has been developed. The method allows multiharmonic forced response to be calculated for a whole bladed disc using a periodic sector model without any loss of accuracy in calculations and modelling. A rigorous proof of the validity of the reduction of the whole nonlinear structure to a sector is provided. Types of bladed disc forcing for which the method may be applied are formulated. A multiharmonic formulation and a solution technique for equations of motion have been derived for two cases of description for a linear part of the bladed disc model: (i) using sector finite element matrices; (ii) using sector mode shapes and frequencies. Calculations validating the developed method and a numerical investigation of a realistic high-pressure turbine bladed disc with shrouds have demonstrated the high efficiency of the method.
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Petrov, E. P., and D. J. Ewins. "Effects of Damping and Varying Contact Area at Blade-Disc Joints in Forced Response Analysis of Bladed Disc Assemblies." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68936.

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In this paper, an approach is developed to analyse the multiharmonic forced response of large-scale finite element models of bladed discs taking account of the nonlinear forces acting at the contact interfaces of blade roots. Area contact interaction is modelled by area friction contact elements which allow for friction stresses under variable normal load, unilateral contacts, clearances and interferences. Examples of application of the new approach to analysis of root damping and forced response levels are given and numerical investigations of effects of contact conditions at root joints and excitation levels are explored for practical bladed discs.
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Moon, Justin, J. Rafael Pacheco, and Arturo Pacheco-Vega. "Heat Transfer Enhancement in Wavy Micro-Channels Through Multiharmonic Surfaces." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86425.

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In this study, three-dimensional numerical simulations are performed to investigate heat transfer enhancement in multi-harmonic micro-scale wavy channels. The focus is on the influence of channel surface-topography, modeled as multi-harmonic sinusoidal waves of square cross-sectional area, on the enhancing mechanisms. A single-wave device of 0.5 mm × 0.5 mm × 20 mm length, is used as baseline, and new designs are built with harmonic-type surfaces. The channel is enclosed by a solid block, with the bottom surface within the sinusoidal region being exposed to a 47 W/cm2 heat flux. The numerical solutions of the governing equations for an incompressible laminar flow and conjugate heat transfer are obtained via finite elements. By using the ratio of the Nusselt number for wavy to straight channels, a parametric analysis — for a set of cold-water flowrates (Re = 50, 100, and 150) — shows that the addition of harmonic surfaces enhances the transfer of energy and that such ratio achieves the highest value with wave harmonic numbers of n = ±2. Use of a performance factor (PF), defined as the ratio of the Nusselt number to the pressure drop, shows that, surprisingly, the proposed wavy multi-harmonic channels are not as efficient as the single-wave geometries. This outcome is thought to be, primarily, due to the uncertainty associated with the definition of the Nusselt number used in this study, and establishes a direction to investigate the development of a more accurate definition.
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Petrov, E. P. "Analysis of Bifurcations in Multiharmonic Analysis of Nonlinear Forced Vibrations of Gas-Turbine Engine Structures With Friction and Gaps." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43670.

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An efficient frequency-domain method has been developed to analyse the forced response of large-scale nonlinear gas-turbine structures with bifurcations. The method allows: detection and localization of the design and operating conditions sets where bifurcations occur; calculation of tangents to the solution trajectory and continuation of solutions under parameter variation for structures with bifurcations. The method is aimed at calculation of steady-state periodic solution and multiharmonic representation of the variation of displacements in time is used. The possibility of bifurcations in realistic gas-turbine structures with friction contacts and with cubic nonlinearity has been shown.
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Chlewicki, Wojciech, Mikolaj Baranowski, Tomasz Czechowski, and Piotr Szczepanik. "Performance of image reconstrucion algorithms in electron paramagnetic resonance tomography with multiharmonic analysis." In 2017 IEEE 37th International Conference on Electronics and Nanotechnology (ELNANO). IEEE, 2017. http://dx.doi.org/10.1109/elnano.2017.7939765.

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Petrov, E. P. "Multiharmonic Analysis of Nonlinear Whole Engine Dynamics With Bladed Disc-Casing Rubbing Contacts." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68474.

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A method has been developed for frequency domain analysis of steady state forced response in gas turbine engines in the presence of rubbing and snubbing contacts between bladed discs and casing and between other rotor and stator engine components. The multiharmonic contact interface elements have been derived for modelling the nonlinear contact interactions: (i) at bearings and (ii) bladed disc-casing rubbing contacts with using flexible models for rotor and stator structures. The elements allow for the asymmetry of the casing, the discrete blade contacts with casing, individual blade-casing gap values, nonlinear dependency of the contact forces on rotor-stator incursion and friction forces, intermittent contacts between blades and the casing. High accuracy and computational efficiency of the methods and models developed has been demonstrated on a set of test cases and on an example of analysis of a realistic gas turbine structure.
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Siewert, Christian, Lars Panning, Jo¨rg Wallaschek, and Christoph Richter. "Multiharmonic Forced Response Analysis of a Turbine Blading Coupled by Nonlinear Contact Forces." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59201.

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The rotor blades of a low pressure (LP) steam turbine stage are subjected to high static and dynamic loads during operation. The static loads are mainly due to the centrifugal force and thermal strains, whereas the dynamic loads are caused by fluctuating gas forces resulting in forced vibrations of the blades. The forced vibrations can lead to high cycle fatigue (HCF) failures causing substantial damage and high maintenance effort. Thus, one of the main tasks in the design of LP steam turbine blading is the vibration amplitude reduction in order to avoid high dynamic stresses that could damage the blading. The vibration amplitudes of the blades in a LP steam turbine stage can be reduced significantly to a reasonable amount if adjacent blades are coupled by shroud contacts that reinforce the blading, see Fig. 1. Furthermore, in the case of blade vibrations, relative displacements between neighboring blades occur in the contacts and friction forces are generated that provide additional damping to the structure due to the energy dissipation caused by micro- and macroslip effects. Therefore, the coupling of the blades increases the overall mechanical damping. A three-dimensional structural dynamics model including an appropriate spatial contact model is necessary to predict the contact forces generated by the shroud contacts and to describe the vibrational behavior of the blading with sufficient accuracy. To compute the nonlinear forced vibrations of the coupled blading, the nonlinear equations of motion are solved in the frequency domain owing to the high computational efficiency of this approach. The transformation of the nonlinear equations of motion into the frequency domain can be carried out by representing the steady-state displacement in terms of its harmonic components. After that transformation, the nonlinear forced response is computed as a function of the excitation frequency in the frequency domain.
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Petrov, E. P. "Sensitivity Analysis of Nonlinear Forced Response for Bladed Discs With Friction Contact Interfaces." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68935.

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An effective method is proposed to calculate sensitivity of nonlinear forced response levels for bladed discs with friction contact interfaces to variation of parameters of these interfaces, including clearances and interferences. First and second order sensitivity coefficients together with ranges of high fidelity for forced response and the sensitivity coefficients prediction are determined. Numerical investigations of the sensitivity of the multiharmonic steady-state forced response of bladed discs with friction contacts and gaps have been performed showing the capabilities and efficiency of the method proposed.
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