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Relevant bibliographies by topics / Non-axisymmetric oscillations

Academic literature on the topic 'Non-axisymmetric oscillations'

Author: Grafiati

Published: 6 September 2023

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Journal articles on the topic "Non-axisymmetric oscillations"

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Sanz, A., and J. Lopez Diez. "Non-axisymmetric oscillations of liquid bridges." Journal of Fluid Mechanics 205, no. -1 (August 1989): 503. http://dx.doi.org/10.1017/s0022112089002120.

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Sotani, Hajime, and Kostas D. Kokkotas. "Non-axisymmetric Torsional Oscillations of Relativistic Stars." Journal of Physics: Conference Series 314 (September 22, 2011): 012081. http://dx.doi.org/10.1088/1742-6596/314/1/012081.

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Dymova, M. V., and M. S. Ruderman. "Non-Axisymmetric Oscillations of Thin Prominence Fibrils." Solar Physics 229, no. 1 (June 2005): 79–94. http://dx.doi.org/10.1007/s11207-005-5002-x.

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Lyubimov, D. V., T. P. Lyubimova, and S. V. Shklyaev. "Non-axisymmetric oscillations of a hemispherical drop." Fluid Dynamics 39, no. 6 (November 2004): 851–62. http://dx.doi.org/10.1007/s10697-004-0002-3.

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Lyubimov, D. V., T. P. Lyubimova, and S. V. Shklyaev. "Non-axisymmetric oscillations of a hemispherical drop." Fluid Dynamics 39, no. 6 (November 2004): 851–62. http://dx.doi.org/10.1007/s10697-005-0021-8.

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Khudainazarov, Sh, B. Donayev, and J. Yarashov. "Non-stationary oscillations of high-rise axisymmetric structures." IOP Conference Series: Materials Science and Engineering 883 (July 21, 2020): 012195. http://dx.doi.org/10.1088/1757-899x/883/1/012195.

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Ruderman, Michael S. "Non-axisymmetric oscillations of thin twisted magnetic tubes." Proceedings of the International Astronomical Union 3, S247 (September 2007): 344–50. http://dx.doi.org/10.1017/s1743921308015068.

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AbstractIn this paper we study non-axisymmetric oscillations of thin twisted magnetic tubes taking the density variation along the tube into account. We use the approximation of the zero-beta plasma. The magnetic field outside the tube is straight and homogeneous, however it is twisted inside the tube. We assume that the azimuthal component of the magnetic field is proportional to the distance from the tube axis, and that the tube is only weakly twisted, i.e. the ratio of the azimuthal and axial components of the magnetic field is small. Using the asymptotic analysis we show that the eigenmodes and eigenfrequencies of the kink and fluting oscillations are described by a classical Sturm-Liouville problem for a second order ordinary differential equation. The main result is that the twist does not affect the kink mode.

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Narayanan, A. Satya. "Non-Radial Oscillations in an Axisymmetric MHD Incompressible Fluid." International Astronomical Union Colloquium 179 (2000): 361–64. http://dx.doi.org/10.1017/s0252921100064836.

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AbstractIt is well known from Helioseismology that the Sun exhibits oscillations on a global scale, most of which are non-radial in nature. These oscillations help us to get a clear picture of the internal structure of the Sun as has been demonstrated by the theoretical and observational (such as GONG) studies. In this study we formulate the linearised equations of motion for non-radial oscillations by perturbing the MHD equilibrium solution for an axisymmetric incompressible fluid. The fluid motion and the magnetic field are expressed as scalarsU,V,PandT, respectively. In deriving the exact solution for the equilibrium state, we neglect the contribution due to meridional circulation. The perturbed quantitiesU*,V*,P*,r*are written in terms of orthogonal polynomials. A special case of the above formulation and its stability is discussed.

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Bohdan, A. V., O. N. Petryschev, Yu I. Yakymenko Yakymenko, and Yu Yu Yanovskaya. "Non-axisymmetric radial vibrations of thin piezoelectric disks." Electronics and Communications 16, no. 3 (March 28, 2011): 195–99. http://dx.doi.org/10.20535/2312-1807.2011.16.3.266783.

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Lee, Umin, and Hideyuki Saio. "Angular-Momemtum Transfer by Nonradial Oscillations in Massive Main-Sequence Stars." International Astronomical Union Colloquium 137 (1993): 287–89. http://dx.doi.org/10.1017/s0252921100017942.

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Angular mementum distribution is one of the most important factors for stellar structutre and evolution. Among other mechanisms, angular momentum is transfered by non-axisymmetric oscillations (nonradial oscillations). In this mechanism the angular momentum is carried mainly by the Reynolds stress, which is proportional to the product between radial and azimuthal components of oscillation velocity; i.e., (Φ direction is the direction of rotation velocity). In the linear oscillation analysis, the phase difference between and is with A finite value of δ, which arises from excitation or damping of the oscillation, makes the time average of finite. Positive angular momentum is transfered from the driving zone to the damping zone by a prograde mode (Osaki 1986).

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Book chapters on the topic "Non-axisymmetric oscillations"

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Bazilo, Constantine, and Liudmyla Usyk. "Modelling of Piezoelectric Disk Transducers Operated on Non-axisymmetric Oscillations for Biomedical Devices." In Advances in Intelligent Systems and Computing, 191–200. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-67133-4_18.

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Yudin, A. S. "Oscillation Equations for Non-axisymmetric Shells." In Springer Proceedings in Materials, 305–20. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-76481-4_26.

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Conference papers on the topic "Non-axisymmetric oscillations"

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CHAKRABARTI, SANDIP K., D. DEBNATH, P. S. PAL, A. NANDI, R. SARKAR, M. M. SAMANTA, P. J. WIITA, H. GHOSH, and D. SOM. "QUASIPERIODIC OSCILLATIONS DUE TO AXISYMMETRIC AND NON-AXISYMMETRIC SHOCK OSCILLATIONS IN BLACK HOLE ACCRETION." In Proceedings of the MG11 Meeting on General Relativity. World Scientific Publishing Company, 2008. http://dx.doi.org/10.1142/9789812834300_0023.

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Bansal, Shubhi, and Prosenjit Sen. "Non-axisymmetric oscillations of droplets in electrowetting-on-dielectric." In 2014 IEEE 2nd International Conference on Emerging Electronics (ICEE). IEEE, 2014. http://dx.doi.org/10.1109/icemelec.2014.7151209.

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Acharya, Vishal, and Timothy Lieuwen. "Response of Non-Axisymmetric Premixed, Swirl Flames to Helical Disturbances." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-27059.

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Flow oscillations associated with hydrodynamic instabilities comprise a key element of the feedback loop during self-excited combustion driven oscillations. This work is motivated in particular by the question of how to scale thermoacoustic stability results from single nozzle or sector combustors to full scale systems. Specifically, this paper considers the response of non-axisymmetric flames to helical flow disturbances of the form u^i′∝expimθ where m denotes the helical mode number. This work closely follows prior studies of the response of axisymmetric flames to helical disturbances. In that case, helical modes induce strong flame wrinkling, but only the axisymmetric, m = 0 mode, leads to fluctuations in overall flame surface area and, therefore, heat release. All other helical modes induce local area/heat release fluctuations with azimuthal phase variations that cancel each other out when integrated over all azimuthal angles. However, in the case of mean flame non-axisymmetries, the azimuthal deviations on the mean flame surface inhibit such cancellations and the asymmetric helical modes (m ≠ 0) cause a finite global flame response. In this paper, a theoretical framework for non-axisymmetric flames is developed and used to illustrate how the flame shape influences which helical modes lead to net flame surface area fluctuations. Example results are presented which illustrate the contributions made by these asymmetric helical modes to the global flame response and how this varies with different control parameters such as degree of asymmetry in the mean flame shape or Strouhal number. Thus, significantly different sensitivities may be observed in single and multi-nozzle flames in otherwise identical hardware in flows with strong helical disturbances, if there are significant deviations in time averaged flame shape between the two, particularly if one of the cases is nearly axisymmetric.

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Culler, Wyatt, Xiaoling Chen, Stephen Peluso, Domenic Santavicca, Jacqueline O’Connor, and David Noble. "Comparison of Center Nozzle Staging to Outer Nozzle Staging in a Multi-Flame Combustor." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75423.

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Combustion instability in gas turbines is often mitigated using fuel staging, a strategy where the fuel is split unevenly between different nozzles of a multiple-nozzle combustor. This work examines the efficacy of different fuel staging configurations by comparing axisymmetric and non-axisymmetric fuel staging in a four-around-one model gas turbine combustor. Fuel staging is accomplished by increasing the equivalence ratio of the center nozzle (axisymmetric staging) or an outer nozzle (non-axisymmetric staging). When the global equivalence ratio is ϕ = 0.70 and all nozzles are fueled equally, the combustor undergoes longitudinal, self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased above ϕStaging = 0.79. This bifurcation equivalence ratio varies between ϕStaging = 0.86 and ϕStaging = 0.76 for the outer nozzles, and is attributed to minor hardware differences between each nozzle. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the staged flame has similar phase relationships for all staging configurations. It is found that axisymmetric staging can be as effective as non-axisymmetric staging; however, the aforementioned hardware variations can impact both the bifurcation equivalence ratio and the effectiveness of staging.

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Khorasany, Ramin M. H., and Stanley G. Hutton. "On the Frequency Response of an Axisymmetric Non-Flat Spinning Disk." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23708.

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For rotating disks, the effect of axisymmetric runout is of interest. This study examines the frequency characteristics of thin rotating discs subjected to axisymmetric non-flatness. The equations of motion used are based on Von Karman’s plate theory. First, the eigenfunctions of the stationary disk problem corresponding to the stress function and transverse displacement are found. These eigenfunctions produce an equation that can be used in the Gelrkin’s method. The initial nonflatness is assumed to be a linear combination of the eigenfunctions of the transverse displacement of the stationary disk problem. Since the initial non-flatness is assumed to be axisymmetric, only eigenfunctions with no nodal diameters are considered to approximate the initial runout. It is supposed that the disk bending deflection is small compared to disk thickness, so we can ignore the second-order terms in the governing equations corresponding to transverse displacement and stress function. After simplifying and discretizing the governing equations of motion, we can obtain a set of coupled equations of motion which takes the effect of initial axisymmetric runout into account. These equations are then used to study the effect of initial runout on the frequency response of the stationary disk. It is found that the initial runout increases the frequencies of the oscillations of a stationary disk. In the next step, we study the effect of initial non-flatness on the critical speed behavior of a spinning disk.

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Subramanian, Harish G., Kiran Manoharan, and Santosh Hemchandra. "Influence of Non-Axisymmetric Confinement on the Hydrodynamic Stability of Multi-Nozzle Swirl Flows." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76368.

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Interaction between coherent flow oscillations and the pre-mixed flame sheet in combustors can result in coherent unsteadiness in the global heat release response. These coherent flow oscillations can either be self-excited (eg. the Precessing Vortex Core) or result from the hydrodynamic response of the flow field to acoustic forcing. Recent work has focused on understanding the various instability modes and fundamental mechanisms that control hydrodynamic instability in single nozzle swirl flows. However, the effect of multiple closely spaced nozzles as well as the non-axisymmetric nature of the confinement imposed by the combustor liner on swirl nozzle flows remains as yet unexplored. We study the influence of inter-nozzle spacing and non-axisymmetric confinement on the local temporal and spatiotemporal stability characteristics of multi-nozzle flows in this paper. The base flow model for the multi nozzle case is constructed by superposing contributions from a base flow model for each individual nozzle. The influence of the flame is captured by specifying a spatially varying base flow density field. The non-axisymmetric local stability problem is posed in terms of a parallel base flow with spatial variations in the two directions perpendicular to the streamwise direction. We investigate the case of a single nozzle and three nozzles arranged in a straight line within a rectangular combustor. The results show that geometric confinement imposed by the combustor walls has a quantitative impact on the eigenvalues of the hydrodynamic modes. Decreasing nozzle spacing for a given geometric confinement configuration makes the flow more unstable. The presence of an inner shear layer stabilized flame results in an overall stabilization of the flow instability. We also discuss qualitatively, the underlying vorticity dynamics mechanisms that influence the characteristics of instability modes in triple nozzle flows.

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Selver, R., Y. Kamotani, and S. Ostrach. "Natural Convection of a Liquid Metal in Vertical Circular Cylinders Heated Locally From Side." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0085.

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Abstract An experimental study is made of natural convection in gallium melts enclosed by vertical circular cylinders with localized heating from the circumference. The heating is done at the mid-height, and the both ends of the cylinder are cooled. The cylinder aspect (Ar = height/diameter) ratio ranges from 2 to 10, and the Rayleigh number (Ra) ranges from 9.0 × 104 to 3.0 × 107. The Prandtl number is 0.021. Temperature measurements are made at six levels along the circumference of the cylinder to study the thermal convection in the melt. Numerical analysis is also conducted to supplement the experimental information. When Ra is small, the melt is in steady toroidal motion. Above a certain Ra the flow becomes non-axisymmetric as a result of a thermal instability in the case of Ar larger than 3. With increasing Ra the motion becomes oscillatory mainly in the upper-half. When Ar is smaller than 3, the toroidal flow becomes non-axisymmetric and oscillatory at the same time beyond a certain Ra. The conditions for the appearance of oscillations and the oscillation frequencies are investigated in detail.

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Dunn, Dwain, Glen Snedden, Theodor von Backström, and Mthobisi P. Mdluli. "Unsteady Effects of a Generic Non-Axisymmetric Endwall Contour on the Rotor of a 1½ Stage Low Speed Turbine Test Rig." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94961.

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Non-axisymmetric endwall contouring has been used as means to improve the characteristics of the flow field exiting a turbine blade row reducing the secondary flows and thus also the secondary losses. The development of non-axisymmetric endwalls has predominantly been done using CFD and detailed measurements in cascades. It has been shown by several researchers that contouring can improve the performance of a gas turbine engine; however the mechanisms that create the improvement are still not fully understood. The current investigation was aimed at unsteady features, if any, and how the unsteady flow field is altered by a non-axisymmetric endwall contour. A previous steady state investigation found that the contouring improved the rotor efficiency of the current rig by 0.4%. The current investigation is an initial experimental investigation into the unsteady nature of the flow in a turbine that has endwdall contours. The unsteady nature of the rotor exit flow field was investigated using an X-film probe to determine if the contouring affected the flow field in ways that the steady measurement technique could not determine. Contour plots, variation in quantities as well as FFT’s were investigated. The unsteady data shows several differences in the flow field of the annular and contoured rotor exit. The velocity range was reduced specifically in the endwall secondary flow region, but the oscillations in the tip leakage flow region were increased. Pitch wise averaged velocity data showed a decrease in the magnitude of the FFT at the blade passing frequency, with the first and second harmonics also being affected. The velocity contours at the rotor exit reveal that the rotor outlet flow field has been made more homogenous (more aligned with the bulk flow) with the addition of the non-axisymmetric endwall contouring.

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Antao, Dion Savio, and Bakhtier Farouk. "Un-Shocked High Amplitude Standing Waves in Wave-Shaped Resonators." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88982.

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A numerical study of non-linear, high amplitude standing waves in non-cylindrical circular resonators is reported here. These waves are shock-less and can generate peak acoustic overpressures that can exceed the ambient pressure by three/four times its nominal value. A high fidelity compressible computational fluid dynamic model is used to simulate the phenomena in cylindrical and arbitrarily shaped axisymmetric resonators. A right circular cylinder and frustum of cone are the two geometries studied. The model is validated using past numerical and experimental results of standing waves in cylindrical resonators. The non-linear nature of the harmonic response of the frustum of cone resonator system is investigated for two different working fluids (carbon dioxide and argon) operating at various values of piston amplitude. The high amplitude non-linear oscillations demonstrated can be used as a prime mover in a variety of applications including thermoacoustic cryocooling.

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Farago, Zoltan, and Norman Chigier. "Parametric Experiments on Coaxial Airblast Jet Atomization." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-081.

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Experiments using high speed, high magnification, and high contrast photography on airblast coaxial atomizers were carried out to study the wave characteristics of liquid surfaces, ligament breakup, and droplet formation. Liquid flow rate was changed from 4 to 50 kg/h, corresponding to a velocity range of 1.5 to 18 m/s, and a Reynolds number range of 1400 to 18000. Air flow rate was varied from 8 to 70 kg/h, corresponding to a velocity range of 22 to 180 m/s, and a Reynolds number range of 13000 to 105000. Tube wall thicknesses of 145 and 320 microns were used. Under different flow conditions, different jet instabilities (capillary, helical and Kelvin-Helmholtz) and different dominant mechanisms of ligament formation were observed. One of the most surprising experimental results is that, under certain flow conditions, the coaxial round liquid jet, surrounded by an axisymmetric annular air stream, forms a flat curling liquid sheet. This liquid sheet breaks into droplet clouds with a frequency of a few thousand Hertz and emits strong oscillations and fluctuating, highly non-axisymmetric vibrations.

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