Relevant bibliographies by topics / Hydrodynamics linear stability analysis

Academic literature on the topic 'Hydrodynamics linear stability analysis'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Hydrodynamics linear stability analysis"

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VOLPERT, V. A., and A. I. VOLPERT. "Convective instability of reaction fronts: Linear stability analysis." European Journal of Applied Mathematics 9, no. 5 (October 1998): 507–25. http://dx.doi.org/10.1017/s095679259800357x.

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The paper is devoted to convective instability of reaction fronts. New approaches are developed to study some eigenvalue problems arising in chemical hydrodynamics. For gaseous combustion in the case of equality of transport coefficients, a linear stability analysis of an upward propagating front is carried out. A minimax representation of the stability boundary is obtained.
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Christian Oliver, Paschereit, Terhaar Steffen, Cosic Bernhard, and Oberleithner Kilian. "IL05 Application of Linear Hydrodynamic Stability Analysis to Reacting Swirling Combustor Flows." Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2013.4 (2013): _IL05–1_—_IL05–11_. http://dx.doi.org/10.1299/jsmeicjwsf.2013.4._il05-1_.

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Khayat, Roger E., and Byung Chan Eu. "Generalized hydrodynamics and linear stability analysis of cylindrical Couette flow of a dilute Lennard–Jones fluid." Canadian Journal of Physics 71, no. 11-12 (November 1, 1993): 518–36. http://dx.doi.org/10.1139/p93-081.

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Linear stability analysis is carried out for cylindrical Couette flow of a Lennard–Jones fluid in the density range from the dense liquid to the dilute gas regime. Generalized hydrodynamic equations are used to calculate marginal stability curves and compare them with those obtained by using the Navier–Stokes–Fourier equations for compressible fluids and also for incompressible fluids. In the low Reynolds or Mach number regime, if the Knudsen number is sufficiently low, the marginal stability curves calculated by the generalized hydrodynamic theory coincide, within numerical errors, with those based on the Navier–Stokes theory. But there are considerable deviations between them in the regimes beyond those mentioned earlier, since nonlinear effects manifest themselves in the laminar mean flow through the nonlinear dissipation term and normal stresses. There are three marginal stability curves obtained in contrast to the Navier–Stokes theory, which yields only two. The previously observed phase-transition-like behavior in fluid variables and the slip phenomenon are found to occur beyond the hydrodynamic stability point. The disturbance entropy production associated with the Taylor–Couette vortices is calculated to first order in disturbances in flow variables and is found to decrease as the number of vortices increases and thereby the dynamic structure is progressively more organized.
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Vanderhaegen, Guillaume, Corentin Naveau, Pascal Szriftgiser, Alexandre Kudlinski, Matteo Conforti, Arnaud Mussot, Miguel Onorato, Stefano Trillo, Amin Chabchoub, and Nail Akhmediev. "“Extraordinary” modulation instability in optics and hydrodynamics." Proceedings of the National Academy of Sciences 118, no. 14 (March 31, 2021): e2019348118. http://dx.doi.org/10.1073/pnas.2019348118.

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The classical theory of modulation instability (MI) attributed to Bespalov–Talanov in optics and Benjamin–Feir for water waves is just a linear approximation of nonlinear effects and has limitations that have been corrected using the exact weakly nonlinear theory of wave propagation. We report results of experiments in both optics and hydrodynamics, which are in excellent agreement with nonlinear theory. These observations clearly demonstrate that MI has a wider band of unstable frequencies than predicted by the linear stability analysis. The range of areas where the nonlinear theory of MI can be applied is actually much larger than considered here.
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Albert, C., A. Tezuka, and D. Bothe. "Global linear stability analysis of falling films with inlet and outlet." Journal of Fluid Mechanics 745 (March 24, 2014): 444–86. http://dx.doi.org/10.1017/jfm.2014.57.

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AbstractIn this paper, the stability of falling films with different flow conditions at the inlet is studied. This is done with an algorithm for the numerical investigation of stability of steady-state solutions to dynamical systems, which is based on an Arnoldi-type iteration. It is shown how this algorithm can be applied to free boundary problems in hydrodynamics. A volume-of-fluid solver is employed to predict the time evolution of perturbations to the steady state. The method is validated by comparison to data from temporal and spatial stability theory, and to experimental results. The algorithm is used to analyse the flow fields of falling films with inlet and outlet, taking the inhomogeneity caused by different inlet conditions into account. In particular, steady states with a curved interface are analysed. A variety of reasonable inlet conditions is investigated. The instability of the film is convective and perturbations at the inlet could be of importance since they are exponentially amplified as they are transported downstream. However, the employed algorithm shows that there is no significant effect of the inlet condition. It is concluded that the flow characteristics of falling films are stable with respect to the considered time-independent inlet conditions.
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Gong, Jinchou, Changxi Ma, and Chenqiang Zhu. "A modified two-lane lattice hydrodynamics model considering the downstream traffic conditions." Modern Physics Letters B 34, no. 24 (June 4, 2020): 2050250. http://dx.doi.org/10.1142/s0217984920502504.

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The difference between the optimal current difference and the actual current difference will be used as the correction item. The dynamic multiple current information about the front lattice will be considered. A modified lattice traffic hydrodynamics model is established by considering the downstream traffic conditions in the two-lane system. Through the stability analysis, it is found that the downstream traffic condition can be added as a correction term to increase the stability of the system. The area of the stable region on the phase diagram is enlarged by the derived stability. The mKdV equation, which can describe density wave, is derived by nonlinear analysis. Finally, the phase diagram of stability condition in linear analysis and the kink wave diagram of mKdV equation in nonlinear analysis are obtained by numerical simulation, which verifies the theoretical derivation of this paper. The results show that in the two-lane traffic flow expansion model, considering the downstream traffic conditions can effectively suppress traffic jams and make the traffic flow stable.
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Hernandez-Duenas, Gerardo, Leslie M. Smith, and Samuel N. Stechmann. "Stability and Instability Criteria for Idealized Precipitating Hydrodynamics." Journal of the Atmospheric Sciences 72, no. 6 (May 27, 2015): 2379–93. http://dx.doi.org/10.1175/jas-d-14-0317.1.

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Abstract A linear stability analysis is presented for fluid dynamics with water vapor and precipitation, where the precipitation falls relative to the fluid at speed VT. The aim is to bridge two extreme cases by considering the full range of VT values: (i) VT = 0, (ii) finite VT, and (iii) infinitely fast VT. In each case, a saturated precipitating atmosphere is considered, and the sufficient conditions for stability and instability are identified. Furthermore, each condition is linked to a thermodynamic variable: either a variable θs, which denotes the saturated potential temperature, or the equivalent potential temperature θe. When VT is finite, separate sufficient conditions are identified for stability versus instability: dθe/dz > 0 versus dθs/dz < 0, respectively. When VT = 0, the criterion dθs/dz = 0 is the single boundary that separates the stable and unstable conditions; and when VT is infinitely fast, the criterion dθe/dz = 0 is the single boundary. Asymptotics are used to analytically characterize the infinitely fast VT case, in addition to numerical results. Also, the small-VT limit is identified as a singular limit; that is, the cases of VT = 0 and small VT are fundamentally different. An energy principle is also presented for each case of VT, and the form of the energy identifies the stability parameter: either dθs/dz or dθe/dz. Results for finite VT have some resemblance to the notion of conditional instability: separate sufficient conditions exist for stability versus instability, with an intermediate range of environmental states where stability or instability is not definitive.
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GERKEMA, THEO. "A linear stability analysis of tidally generated sand waves." Journal of Fluid Mechanics 417 (August 25, 2000): 303–22. http://dx.doi.org/10.1017/s0022112000001105.

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A linear stability analysis is carried out to examine the initial stage of sand-wave growth under tidal flows and the occurrence of a preferred length scale. The fact that these bedforms typically have length scales small compared to the tidal excursion is exploited by adopting an asymptotic approach to solve the hydrodynamic part of the problem, i.e. to find the hydrodynamic response to an initially small bed perturbation. This method is shown to have important advantages over previously used methods, since it allows an exploration of the complete sand-wave regime (whereas other methods fail for short sand waves), and in general it is also more accurate. It is found that the selection of a preferred length scale depends mainly on only two parameters (the bed-slope coefficient, and the ratio of friction velocity to eddy viscosity), whereas there appears to be almost no dependence on the water depth.
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Jiang, Zhongzheng, Wenwen Zhao, Weifang Chen, and Zhenyu Yuan. "Eu's generalized hydrodynamics with its derived constitutive model: Comparison to Grad's method and linear stability analysis." Physics of Fluids 33, no. 12 (December 2021): 127116. http://dx.doi.org/10.1063/5.0071715.

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Das, S., S. K. Guha, and A. K. Chattopadhyay. "Linear stability analysis of hydrodynamic journal bearings under micropolar lubrication." Tribology International 38, no. 5 (May 2005): 500–507. http://dx.doi.org/10.1016/j.triboint.2004.08.023.

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Dissertations / Theses on the topic "Hydrodynamics linear stability analysis"

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Hadley, Kathryn Z. 1955. "Linear stability analysis of nonaxisymmetric instabilities in self-gravitating polytropic disks." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11253.

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xvii, 371 p. : col. ill.
An important problem in astrophysics involves understanding the formation of planetary systems. When a star-forming cloud collapses under gravity its rotation causes it to flatten into a disk. Only a small percentage of the matter near the rotation axis falls inward to create the central object, yet our Sun contains over 99% of the matter of our Solar System. We examine how global hydrodynamic instabilities transport angular momentum through the disk causing material to accrete onto the central star. We analyze the stability of polytropic disks in the linear regime. A power law angular velocity of power q is imposed, and the equilibrium disk structure is found through solution of the time-independent hydrodynamic equations via the Hachisu self-consistent field method. The disk is perturbed, and the time-dependent linearized hydrodynamic equations are used to evolve it. If the system is unstable, the characteristic growth rate and frequency of the perturbation are calculated. We consider modes with azimuthal e im[varphi] dependence, where m is an integer and [varphi] is the azimuthal angle. We map trends across a wide parameter space by varying m , q and the ratios of the star-to-disk mass M * /M d and inner-to-outer disk radius r - /r + . We find that low m modes dominate for small r - /r + , increasing to higher r - /r + as M * /M d increases, independent of q . Three main realms of behavior are identified, for M * << M d , M * [approximate] M d and M * >> M d , and analyzed with respect to the I, J and P mode types as discussed in the literature. Analysis shows that for M * << M d , small r - /r + disks are dominated by low m I modes, which give way to high m J modes at high r - /r + . Low m J modes dominate M * [approximate] M d disks for small r - /r + , while higher m I modes dominate for high r - /r + . Behavior diverges with q for M * >> M d systems with high q models approximating M * [approximate] M d characteristics, while low q models exhibit m = 2 I modes dominating where r - /r + < 0.60.
Committee in charge: Raymond Frey, Chairperson; James Imamura, Advisor; Robert Zimmerman, Member; Paul Csonka, Member; Alan Rempel, Outside Member
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Tun, Yarzar. "Nonmodal Analysis of Temporal Transverse Shear Instabilities in Shallow Flows." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36886.

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Shallow flows are those whose width is significantly larger than their depth. In these types of flows, two dimensional coherent structures can be generated and can influence the flow greatly by the lateral transfer of mass and momentum. The development of coherent structures as a result of flow instabilities has been a topic of interest for environmental fluid mechanics for decades. Studies on the use of linear modal stability analysis is commonly found in literature. However, the relatively recent development in the field of hydrodynamic stability suggests that the traditional linear modal stability analysis does not describe the behaviour of the perturbations in finite time. The discrepancy between asymptotic behaviour and finite time behaviour is particularly large in shear driven flows and it is most likely to be the case for shallow flows. This study aims to provide a better understanding of finite time growth of perturbation energy in shallow flows. The three cases of shallow flows evaluated are the mixing layer, jet and wake. The critical cases are obtained through the linear modal analysis and nonmodal analysis was conducted to show the transient behaviour in finite time for what is so-called marginally stable. Finally, the thesis concludes by generalizing the finite time energy growth in the S-k space.
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Bridel-Bertomeu, Thibault. "Investigation of unsteady phenomena in rotor/stator cavities using Large Eddy Simulation." Thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17867/1/BRIDEL_BERTOMEU.pdf.

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This thesis provides a numerical and theoretical investigation of transitional and turbulent enclosed rotating flows, with a focus on the formation of macroscopic coherent flow structures. The underlying processes are strongly threedimensional due to the presence of boundary layers on the discs and on the walls of the outer (resp. inner) cylindrical shroud (resp. shaft). The complexity of these flows poses a great challenge in fundamental research however the present work is also of importance for industrial rotating machinery, from hard-drives to space engines turbopumps - the design issues of the latter being behind the motivation for this thesis. The present work consists of two major investigations. First, industrial cavities are modeled by smooth rotor/stator cavities and therein the dominant flow dynamics is investigated. For the experimental campaigns on industrial machinery revealed dangerous unsteady phenomena within the cavities, the emphasis is put on the reproduction and monitoring of unsteady pressure fluctuations within the smooth cavities. Then, the LES of three configurations of real industrial turbines are conducted to study in situ the pressure fluctuations and apply the diagnostics already vetted on academic problems.
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Bengana, Yacine. "Simulations numériques pour la prédiction de fréquences par champs moyens." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLET032.

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Les écoulements fluides jouent un rôle important dans de nombreux phénomènes naturels ainsi que dans de nombreux secteurs industriels. On s’intéresse dans cette thèse aux écoulements instationnaires oscillants provenant d’une bifurcation de Hopf.L’écoulement affleurant une cavité carrée ouverte présente deux cycles limites séparés par un état quasi-périodique instable. Nous avons décrit en détail ce scénario au moyen de simulations numériques directes, de l’analyse de stabilité linéaire et de l’analyse de Floquet. La bifurcation de Hopf dans la geometry de Taylor-Couette donne naissance à deux solutions, les spirals (ondes progressives) et les rubans (ondes stationnaires dans la direction axiale). Nous avons découvert que la branche des rubans est suivie de deux cycles hétéroclines consécutifs avec deux états axisymétriques comme point d’ancrage.L’analyse de stabilité linéaire autour des solutions stationnaires permet d’obtenir le seuil de bifurcation. Une autre approche, est la linéarisation autour du champ moyen. Cette approche permet d’obtenir des fréquences très proches des fréquences non linéaires et montre dans la plupart des cas un taux de croissance proche de zéro. Nous avons montré que les spirales, les rubans, la cavité entrainée ainsi que l’écoulement autour d’un objet prismatique vérifient cette propriété.Dans la convection thermosolutal, la linéarisation autour du champ moyen des ondes stationnaires ne permet pas d’obtenir les fréquences non linéaires et le taux de croissance est loin d’être zéro, par contre pour les ondes progressives cette propriété est pleinement satisfaite. Nous avons étudié la validité d’un modèle auto-cohérent dans le cas de ces ondes progressives. En effet, si l’écoulement vérifie la propriété du champ moyen, ce modèle est supposé calculer le champ moyen, la fréquence nonlinear ainsi que l’amplitude. Ce modèle est constitué de l’équation gouvernant le champ moyen couplé avec l’équation linéarisé au travers le mode le plus instable et des contraintes de Reynolds. Nous avons montré que dans le cas des ondes progressives ce modèle permet de prédire la fréquence non linéaire seulement très proche du seuil. La prédiction est améliorée significativement en considérant les ordres supérieurs dans le terme des contraintes de Reynolds
Fluid flows play an important role in many natural phenomena as well as in many industrial applications. In this thesis, we are interested in oscillating flows origins from a Hopf bifurcation.The open shear-driven square cavity has two limit cycles separated by an unsteady quasi-periodic state. We have described this scenario in detail by using direct numerical simulations, linear stability analysis, and Floquet analysis. The Hopf bifurcation in Taylor-Couette flow gives rise to two solutions, spirals (traveling waves) and ribbons (standing waves in the axial direction). We discovered that the ribbons branch is followed by two consecutive heteroclinic cycles connecting two pairs of axisymmetric vortices. We studied in detail these two heteroclinic cycles.The linear stability analysis about the stationary solution is used to compute the threshold of the bifurcations. Another approach is the linearization about the mean field. This approach gives frequencies very close to that of the nonlinear system and shows in most cases a nearly zero growth rate. We have shown that spirals, ribbons, the lid-driven cavity and the flow around a prismatic object verify this property.In the thermosolutal convection, the frequencies obtained by the linearization about the mean field of the standing waves do not match the nonlinear frequencies and the growth rate is far from zero, on the other hand for the traveling waves this property is fully satisfied. We studied the validity of a self-consistent model in the case of the traveling waves. The self-consistent model consists of the mean field governing equation coupled with the linearized Navier-Stokes equation through the most unstable mode and the Reynolds stress term. This model calculates the mean field, the nonlinear frequency, and the amplitude without time integration. The self-consistent model is assumed to be valid for flows that satisfy the property of the mean field. We have shown that in this case, this model predicts the nonlinear frequency only very close to the threshold. We have improved significantly the predictions by considering higher orders in the Reynolds stress term
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Zhang, Mengqi. "Linear stability Analysis of Viscoelastic Flows." Thesis, KTH, Mekanik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95137.

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The goal of present work is to investigate the instability of jet ow, mixing layer and Poiseuille ow of viscoelastic uids. According to Boeta et al: [4], small elastic eect in Kolmogorov ow will result in increasing critical Re for hydrodynamic instability, however, at high elasticity a new instability of elastic nature occurs even at vanishing Re. This thesis aims to test this result in jet and mixing layer. In addition, linear stability analysis (modal and non-modal) of viscoelastic Poiseuille ow is carried out to understand the elastic eects on the ows of both Oldroyd-B and FENE-P model uids. Energy analysis is used to reveal the instability mechanism.
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Hu, Bin. "Stability analysis of linear thin shells." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7360/.

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Shell structure is widely used in engineering area. The purpose of this dissertation is to show the behavior of a thin shell under external load, especially for long cylindrical shell under compressive load, I analyzed not only for linear elastic problem and also for buckling problem, and by using finite element analysis it shows that the imperfection of a cylinder could affect the critical load which means the buckling capability of this cylinder. For linear elastic problem, I compared the theoretical results with the results got from Straus7 and Abaqus, and the results are really close. For the buckling problem I did the same: compared the theoretical and Abaqus results, the error is less than 1%, but in reality, it’s not possible to reach the theoretical buckling capability due to the imperfection of the cylinder, so I put different imperfection for the cylinder in Abaqus, and found out that with the increasing of the percentage of imperfection, the buckling capability decreases, for example 10% imperfection could decrease 40% of the buckling capability, and the outcome meet the buckling behavior in reality.
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VALERIO, JULIANA VIANNA. "LINEAR STABILITY ANALYSIS OF VISCOUS AND VISCOELASTIC FLOWS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=10021@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
As informações sobre a sensibilidade da solução de um dado escoamento mediante a perturbações infinitesimais é importante para o seu completo entendimento. A análise de estabilidade de escoamentos pode ser utilizada na otimização de processos industriais. Na indústria de revestimento o controle da estabilidade é fundamental, uma vez que o escoamento na região de aplicação da camada de líquido sobre o substrato, de um modo geral, tem que ser laminar, bidimensional e em regime permanente. O objetive é determinar, dentro do espaço de parâmetros de operação, a região onde o escoamento é estável e conseqüêntemente a camada a ser revestida uniforme. Porém, por ser uma análise complexa, só é usada na indústria em estudos mais apurados. O sistema linear que descreve a estabilidade vai ser discretizado com o método de Galerkin / elementos finitos, dando origem a um problema de autovalor generalizado.Tanto para escoamentos com líquidos newtonianos como para escoamentos com líquidos viscoelásticos, uma das matrizes do problema de autovalor generalizado é singular e alguns autovalores se encontram no infinito. No escoamento com líquidos viscoelásticos parte do espectro é contínuo, aumentando o grau de dificuldade da análise numérica para encontrá-lo. Nesse trabalho, vamos apresentar um método baseado em transformações lineares tirando vantagem das estruturas matriciais e transformando-as em um problema de autovalor clássico com dimens são, pelo menos, três vezes menor que o original. O método elimina os autovalores infinitos do problema com um baixo custo computacional. A estabilidade de um escoamento de Couette unidimensional de líquido newtoniano é analisada como um primeiro exemplo. Depois, o início do estudo da estabilidade em um escoamento de Couette bidimensional e também um escoamento pistonado com o mesmo líquido. Generaliza-se o método para o escoamento de Couette de um líquido viscoelástico, os resultados para o escoamento de um líquido cujo comportamento mecânico é descrito pelo modelo de Maxwell são apresentados e comparados com a solução analítica de Gorodtsov & Leonov, 1967. A relação entre os autovetores do problema transformado e do original é apresentada.
Steady state,two-dimensional flows may become unstable under two and three-dimensional disturbances, if the flow parameters exceed some critical values. In many practical situations, determining the parameters at which the flow becomes unstable is essential. The complete understanding of viscous and viscoelastic flows requires not only the steady state solution of the governing equations, but also its sensitivity to small perturbations. Linear stability analysis leads to a generalized eigenvalue problem, GEVP. Solving the GEVP is challenging, even for Newtonian liquids, because the incompressibility constraint creates singularities that lead to nonphysical eigenvalues at infinity. For viscoelastic flows, the difficulties are even higher because of the continuous spectrum of eigenmodes associated with differential constitutive equations. The complexity and high computational cost of solving the GEVP have probably discouraged the use of linear stability analysis of incompressible flows as a general engineering tool for design and optimization. The Couette flow of UCM liquids has been used as a classical problem to address some of the important issues related to stability analysis of viscoelastic flows. The spectrum consists of two discrete eigenvalues and a continuous segment of eigenvalues with real part equal to -1/We (We is the Weissenberg number). Most of the numerical approximation of the spectrum of viscoelastic Couette flow presented in the literature were obtained using spectral expansions. The eigenvalues close to the continuous part of the spectrum show very slow convergence. In this work, the linear stability of Couette flow of a Newtonian and UCM liquids were studied using finite element method, which makes it easier to extend the analysis to complex flows. A new procedure to eliminate the eigenvalues at infinity from the GEVP that come from differential equations is also proposed. The procedure takes advantage of the structure of the matrices involved and avoids the computational effort of common mapping techniques. With the proposed procedure, the GEVP is transformed into a smaller simple EVP, making the computations more effcient. Reducing the computational memory and time. The relation between the eigenvector from the original problem and the reduced one is also presented.
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Flynn, Terrance J. "Linear stability analysis of a solidifying ternary alloy." Fairfax, VA : George Mason University, 2009. http://hdl.handle.net/1920/4594.

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Thesis (M.S.)--George Mason University, 2009.
Vita: p. 164. Thesis director: Daniel Anderson. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Mathematics. Title from PDF t.p. (viewed Oct. 12, 2009). Includes bibliographical references (p. 163). Also issued in print.
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Fang, Yuguang. "Stability analysis of linear control systems with uncertain parameters." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057598985.

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Beneddine, Samir. "Characterization of unsteady flow behavior by linear stability analysis." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX010/document.

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Au cours des dernières décennies, la théorie de la stabilité a été intensivement utilisée pour caractériser le comportement instationnaire d'écoulements. Cela a donné naissance à un grand nombre d'approches, mais malheureusement chacune d'entre elles semble présenter ses propres limitations. De plus, leurs conditions de validité sont encore très mal connues, ce qui soulève la question de la fiabilité de ce genre de méthodes dans un cas général.Cette problématique est traitée dans cette thèse en s'intéressant dans un premier temps aux approches classiques de stabilité, qui étudient l'évolution de petites perturbations autour d'une solution stationnaire -- un champ de base -- des équations de Navier-Stokes. Pour cela, le phénomène du screech -- un bruit tonal que peuvent causer les jets sous-détendus -- est étudié d'un point de vue de la stabilité linéaire. Les résultats obtenus montrent que la dynamique non-linéaire du phénomène est correctement prédite par une analyse linéaire de stabilité du champ de base. Une confrontation avec d'autres analyses similaires montre qu'un tel résultat n'est pas toujours observé. Cependant, lorsque les oscillations auto-entretenues d'un écoulement sont provoquées par un bouclage acoustique, comme c'est le cas entre autres pour le screech, l'écoulement de cavité ou encore les jets impactants, alors les non-linéarités ont une faible influence sur le phénomène de sélection de fréquence. Cela explique la capacité d'une analyse linéaire à caractériser ces écoulements, même dans le régime non-linéaire.Une autre approche, consistant à étudier la stabilité linéaire du champ moyen, a montré de bons résultats dans certaines configurations qui ne peuvent être correctement étudiées par une analyse linéaire du champ de base. Cela est justifié dans cette thèse en mettant en évidence le rôle que joue la résolvante autour du champ moyen dans la dynamique d'un écoulement. Il est montré que lorsque cet opérateur présente une forte séparation de valeurs singulières, ce qui correspond à l'existence d'un mécanisme d'instabilité fort, alors les modes de Fourier de l'écoulement sont proportionnels aux modes de résolvante dominants. Ce résultat fournit des conditions mathématiques et physiques pour l'utilisation et le sens de diverses méthodes d'analyse du champ moyen, telles qu'une analyse d'équations de stabilité parabolisées (Parabolised Stability Equations). De plus, cela permet de mettre en place un modèle de prédiction du spectre fréquentiel en tout point d'un écoulement, à partir d'une ou de quelques mesures ponctuelles et du champ moyen. L'ensemble de ces résultats est illustré et validé sur un cas de marche descendante turbulente. Enfin, cela est exploité dans un cadre expérimental, afin de reconstruire le comportement instationnaire d'un jet rond transitionnel, à partir de la seule connaissance du champ moyen et d'une mesure ponctuelle. L'étude montre que, sous certaines précautions expérimentales, la reconstruction est très précise et robuste
Linear stability theory has been intensively used over the past decades for the characterization of unsteady flow behaviors. While the existing approaches are numerous, none has the ability to address any general flow. Moreover, clear validity conditions for these techniques are often missing, and this raises the question of their general reliability.In this thesis, this question is addressed by first considering the classical stability approach, which focuses on the evolution of small disturbances about a steady solution -- a base flow -- of the Navier-Stokes equations.To this end, the screech phenomenon -- a tonal noise that is sometimes generated by underexpanded jets -- is studied from alinear stability point of view. The results reveal that the nonlinear dynamics of this phenomenon is well-predicted by a linear base flow stability analysis. A confrontation with other similar analyses from the literature shows that such a satisfactory result is not always observed. However, when a self-sustained oscillating flow is driven by an acoustic feedback loop, as it is the case for the screech phenomenon, cavity flows and impinging jets for instance, then the nonlinearities have a weak impact on the frequency selection process, explaining the ability of a linear analysis to characterize the flow, even in the nonlinear regime.Another alternative approach, based on a linearization about the mean flow, is known to be successful in some cases where a base flow analysis fails. This observation from the literature is explained in this thesis by outlining the role of the resolvent operator, arising from a linearization about the mean flow, in the dynamics of a flow. The main finding is that if this operator displays a clear separation of singular values, which relates to the existence of one strong convective instability mechanism, then the Fourier modes areproportional to the first resolvent modes. This result provides mathematical and physical conditions for the use and meaning of several mean flow stability techniques, such as a parabolised stability equations analysis of a mean flow.Moreover, it leads to a predictive model for the frequency spectrum of a flow field at any arbitrary location, from the sole knowledge of the mean flow and the frequency spectrum at one or more points. All these findings are illustrated and validated in the case of a turbulent backward facing step flow. Finally, these results are exploited in an experimental context, for the reconstruction of the unsteady behavior of a transitional round jet, from the sole knowledge of the mean flow and one point-wise measurement. The study shows that, after following a few experimental precautions, detailed in the manuscript, the reconstruction is very accurate and robust
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Books on the topic "Hydrodynamics linear stability analysis"

1

Rogers, E. T. A. Stability analysis for linear repetitive processes. Berlin: Springer-Verlag, 1992.

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Rogers, Eric, and David H. Owens, eds. Stability Analysis for Linear Repetitive Processes. Berlin/Heidelberg: Springer-Verlag, 1992. http://dx.doi.org/10.1007/bfb0007165.

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Boi͡adzhiev, Khristo. Non-linear mass transfer and hydrodynamic stability. Amsterdam: Elsevier, 2000.

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Shi, Jian. A simplified Von Neumann method for linear stability analysis. Cranfield, Bedford, England: Cranfield Institute of Technology, College of Aeronautics, 1993.

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Aristide, Halanay, ed. Stabilization of linear systems. Boston, MA: Birkhauser, 1999.

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Dragan, Vasile. Stabilization of Linear Systems. Boston, MA: Birkhäuser Boston, 1999.

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Donley, M. G. Dynamic analysis of non-linear structures by the method of statistical quadratization. Berlin: Springer-Verlag, 1990.

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Kopachevskiĭ, N. D. Operator approach to linear problems of hydrodynamics. Basel: Birkhäuser Verlag, 2001.

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Tsamilis, Sotirios E. Nonlinear analysis of coupled roll/sway/yaw stability characteristics of submersible vehicles. Monterey, Calif: Naval Postgraduate School, 1997.

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Graham, Ronald E. Linearization of digital derived rate algorithm for use in linear stability analysis. [Washington, DC?]: National Aeronautics and Space Administration, 1985.

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Book chapters on the topic "Hydrodynamics linear stability analysis"

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Qin, Tongran. "Linear Stability Analysis." In Springer Theses, 125–40. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-61331-4_6.

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Schmid, Peter J., and Dan S. Henningson. "Linear Inviscid Analysis." In Stability and Transition in Shear Flows, 15–53. New York, NY: Springer New York, 2001. http://dx.doi.org/10.1007/978-1-4613-0185-1_2.

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Goberna, Miguel A., and Marco A. López. "Qualitative Stability Analysis." In Post-Optimal Analysis in Linear Semi-Infinite Optimization, 61–77. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4899-8044-1_5.

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Goberna, Miguel A., and Marco A. López. "Quantitative Stability Analysis." In Post-Optimal Analysis in Linear Semi-Infinite Optimization, 79–107. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4899-8044-1_6.

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Joseph, Daniel D., and Yuriko Y. Renardy. "Lubricated Pipelining: Linear Stability Analysis." In Interdisciplinary Applied Mathematics, 17–113. New York, NY: Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4615-7061-5_2.

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Lakshmanan, M., and D. V. Senthilkumar. "Linear Stability and Bifurcation Analysis." In Dynamics of Nonlinear Time-Delay Systems, 17–29. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14938-2_2.

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Vasilyev, F. P., and A. Yu Ivanitskiy. "Criterion of Stability." In In-Depth Analysis of Linear Programming, 167–202. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-015-9759-3_4.

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Dolzhansky, Felix V. "Stating the Linear Stability Problem for Plane-Parallel Flows of Ideal Homogeneous and Nonhomogeneous Fluids." In Fundamentals of Geophysical Hydrodynamics, 117–23. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-31034-8_13.

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Dolzhansky, Felix V. "The Taylor Problem of Stability of Motion of a Stratified Fluid with a Linear Velocity Profile." In Fundamentals of Geophysical Hydrodynamics, 133–39. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-31034-8_15.

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Rust, Wilhelm. "Stability Problems." In Non-Linear Finite Element Analysis in Structural Mechanics, 87–109. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-13380-5_3.

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Conference papers on the topic "Hydrodynamics linear stability analysis"

1

Oberleithner, Kilian, and Christian Oliver Paschereit. "Modeling Flame Describing Functions Based on Hydrodynamic Linear Stability Analysis." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57316.

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Combustion instabilities crucially affect the operational range of modern lean premixed gas turbine combustors and must be avoided or kept at low amplitudes. The main uncertainty of current prediction models is the flame describing function (FDF) that characterizes the flame response to high amplitude acoustic forcing. In this work, we present a new FDF model based on linear hydrodynamic stability analysis. This work is in continuation of an earlier study, where the frequency dependence and saturation of the FDF gain of a perfectly premixed flame was linked to the growth rates of the Kelvin–Helmholtz (KH) instability. In this work, we report on FDF measurements in a newly designed swirl-stabilized combustor. We identify two independent mechanisms that determine the flame response. The first stems from swirl-fluctuations that are generated in the swirler and the second stems from the KH instability. The swirl-fluctuations are approximated by a convective time lag model. The KH instability is predicted from linear hydrodynamic stability analysis based on the time-mean flow measured via PIV. A combination of both models leads to a good quantitative agreement with the measured FDF. Besides the practical advantages of predicting the FDF from stationary flow data, the model reveals the mechanisms driving the saturation of the FDF and guides the way out from the black-box treatment of the nonlinear flame response.
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Das, Subrata, and Sisir Kumar Guha. "Linear stability analysis of hydrodynamic journal bearings operating under turbulent micropolar lubrication." In 2017 International Conference on Advances in Mechanical, Industrial, Automation and Management Systems (AMIAMS). IEEE, 2017. http://dx.doi.org/10.1109/amiams.2017.8069199.

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Ommani, Babak, and Odd M. Faltinsen. "Linear Dynamic Stability Analysis of a Surface Piercing Plate Advancing at High Forward Speed." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-11136.

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The dynamic stability of a surface-piercing plate advancing with high forward speed in horizontal plane is investigated in the scope of linear theory. The hydrodynamic forces on the plate in sway and yaw are presented in terms of frequency and forward speed dependent added mass and damping coefficients. Flow separation from the trailing edge of the plate is considered. A time domain boundary integral method using linear distribution of Rankine sources and dipoles on the plate, free surface and a vortex sheet is used to calculate these hydrodynamic coefficients numerically. Comparison between the current numerical results and previous numerical and experimental results are presented. Using linear dynamic stability analysis the influence of hydrodynamic coefficients on the plate’s stability is investigated as a simplified alternative to a semi-displacement vessel.
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Emmanuel- Douglas, Ibiba. "A Generalized Mathematical Procedure for Ship Motion Stability Analysis." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79041.

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The challenges of providing safe and high performance marine vehicles present strict and often conflicting constraints that require rational and holistic analysis methodologies to obtain efficient design solutions. This paper presents a mathematical framework for stability analysis, which is one of the key elements in the design and operation of ships and floating bodies that still require considerable improvement. The method is based on the application of the Lyapunov stability analysis concept, which has been highly successful in some other engineering and scientific disciplines. The paper presents the fundamental concepts on the applicability of the Lyapunov method to ship motions stability analysis. Governing mathematical models are derived from first principles and interpreted in the context of geometrical and physical interrelationships. The analytical models are primarily developed for the generalized case of non-linear forced non-conservative systems and simplified by linearization in the case of coupled motion for detailed analysis and characterization of stability conditions and domain. The concept of “motion boundedness” is introduced to satisfy requirements of the Lyapunov method to ship motions subjected to continuous excitations. The analysis leads to some valuable deductions and insight that would be useful in the formulation of stability criteria for ships and marine vehicles in general. The most significant contribution is the possibility of explicit determination of geometric and hydrostatics/hydrodynamics parameters that govern ship stability characteristics.
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Kakoty, S. K., S. K. Laha, and P. Mallik. "Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34416.

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A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.
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Kaiser, Thomas L., Thierry Poinsot, and Kilian Oberleithner. "Stability and Sensitivity Analysis of Hydrodynamic Instabilities in Industrial Swirled Injection Systems." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63649.

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The hydrodynamic instability in an industrial, two-staged, counter-rotative, swirled injector of highly complex geometry is under investigation. Large eddy simulations show that the complicated and strongly nonparallel flow field in the injector is superimposed by a strong precessing vortex core. Mean flow fields of large eddy simulations, validated by experimental particle image velocimetry measurements are used as input for both local and global linear stability analysis. It is shown that the origin of the instability is located at the exit plane of the primary injector. Mode shapes of both global and local linear stability analysis are compared to a dynamic mode decomposition based on large eddy simulation snapshots, showing good agreement. The estimated frequencies for the instability are in good agreement with both the experiment and the simulation. Furthermore, the adjoint mode shapes retrieved by the global approach are used to find the best location for periodic forcing in order to control the precessing vortex core.
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Paredes, Pedro, Vassilis Theofilis, Steffen Terhaar, Kilian Oberleithner, and Christian Oliver Paschereit. "Global and Local Hydrodynamic Stability Analysis as a Tool for Combustor Dynamics Modeling." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-44173.

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Coherent flow structures in shear flows are generated by instabilities intrinsic to the hydrodynamic field. In a combustion environment, these structures may interact with the flame and cause unsteady heat release rate fluctuations. Prediction and modeling of these structures is thereby highly wanted for thermo-acoustic prediction models. In this work we apply hydrodynamic linear stability analysis to the time-averaged flow field of swirl-stabilized combustors obtained from experiments. Recent fundamental investigations have shown that the linear eigenmodes of the mean flow accurately represent the growth and saturation of the coherent structures. In this work biglobal and local stability analysis is applied to the reacting flow in an industry-relevant combustion system. Both the local and the biglobal analysis accurately predicts the onset and structure of a self-excited global instability that is known in the combustion community as a precessing vortex core (PVC). However, only the global analysis accurately predicts a globally stable flow field for the case without the oscillation, while the local analysis wrongly predicts an unstable global growth rate. The predicted spatial distribution of the amplitude functions using both analysis agree very well to the experimentally identified global mode. The presented tools are considered as very promising for the understanding of the PVC and physics based flow control.
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Zakarian, Erich. "Stability Analysis of Two-Phase Flows in Pipe-Riser Systems." In 2000 3rd International Pipeline Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/ipc2000-237.

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A differential-algebraic system is presented to model unstable two-phase flows in pipe-riser systems. Equations derive from the space integration of an isothermal drift-flux model assuming quasi-equilibrium momentum balance. A linear analysis of this system gives a new stability criterion for gas-liquid flows in pipe-riser systems. This criterion is validated by laboratory experiments. Then, a nonlinear analysis shows that the severe slugging phenomenon is a hydrodynamic instability coming from a supercritical Hopf bifurcation.
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Tammisola, Outi, and Matthew P. Juniper. "Adjoint Sensitivity Analysis of Hydrodynamic Stability in a Gas Turbine Fuel Injector." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42736.

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Hydrodynamic oscillations in gas turbine fuel injectors help to mix the fuel and air but can also contribute to thermoacoustic instability. Small changes to some parts of a fuel injector greatly affect the frequency and amplitude of these oscillations. These regions can be identified efficiently with adjoint-based sensitivity analysis. This is a linear technique that identifies the region of the flow that causes the oscillation, the regions of the flow that are most sensitive to external forcing, and the regions of the flow that, when altered, have most influence on the oscillation. In this paper, we extend this to the flow from a gas turbine’s single stream radial swirler, which has been extensively studied experimentally (GT2008-50278) [8]. The swirling annular flow enters the combustion chamber and expands to the chamber walls, forming a conical recirculation zone along the centreline and an annular recirculation zone in the upstream corner. In this study, the steady base flow and the stability analysis are calculated at Re 200–3800 based on the mean flow velocity and inlet diameter. The velocity field is similar to that found from experiments and LES, and the local stability results are close to those at higher Re (GT2012-68253) [11]. All the analyses (experiments, LES, uRANS, local stability, and the global stability in this paper) show that a helical motion develops around the central recirculation zone. This develops into a precessing vortex core. The adjoint-based sensitivity analysis reveals that the frequency and growth rate of the oscillation is dictated by conditions just upstream of the central recirculation zone (the wavemaker region). It also reveals that this oscillation is very receptive to forcing at the sharp edges of the injector. In practical situations, this forcing could arise from an impinging acoustic wave, showing that these edges could be influential in the feedback mechanism that causes thermoacoustic instability. The analysis also shows how the growth rate and frequency of the oscillation change with either small shape changes of the nozzle, or additional suction or blowing at the walls of the injector. It reveals that the oscillations originate in a very localized region at the entry to the combustion chamber, which lies near the separation point at the outer inlet, and extends to the outlet of the inner pipe. Any scheme designed to control the frequency and amplitude of the oscillation only needs to change the flow in this localized region.
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Kaiser, Thomas Ludwig, Kilian Oberleithner, Laurent Selle, and Thierry Poinsot. "Examining the Effect of Geometry Changes in Industrial Fuel Injection Systems on Hydrodynamic Structures With BiGlobal Linear Stability Analysis." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90447.

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Abstract Shape optimization with respect to the suppression or enhancement of dynamical flow structures is an important topic in combustion research and beyond. In this paper, we investigate the flow in an industrial fuel injection system by experimental means, as well as Large Eddy Simulation (LES) and Linear Stability Analysis (LSA) for two configurations of the swirler. In the first configuration, the reference geometry, a Precessing Vortex Core (PVC) occurs. In the second configuration, a center body is mounted in the interior of the injector. It is shown by both experiments and LES that the PVC is suppressed in the presence of the center body, while the mean flow remains nearly unaffected. The method of LSA is applied in order to explain the effect of the geometry change. The work shows that LSA is capable of explaining the occurrence or disappearance of coherent structures evolving on the turbulent flows if the geometry is changed. This is an important step in using LSA in the context of shape optimization of industrial fuel injectors.
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Reports on the topic "Hydrodynamics linear stability analysis"

1

Warnock, R. Linear Vlasov Analysis for Stability of a Bunched Beam. Office of Scientific and Technical Information (OSTI), August 2004. http://dx.doi.org/10.2172/829709.

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Hunter, J. H. Hydrodynamics of exploding foils: Progress on similarity solution and a stability analysis for early time. Office of Scientific and Technical Information (OSTI), November 1986. http://dx.doi.org/10.2172/6843111.

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Escobar, D., and E. Ahedo. Global Linear Stability Analysis of the Spoke Oscillation in Hall Effect Thrusters. Fort Belvoir, VA: Defense Technical Information Center, July 2014. http://dx.doi.org/10.21236/ada616022.

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Schunk, Peter Randall, Duane A. Labreche, Matthew M. Hopkins, Amy Cha-Tien Sun, and Ed Wilkes. Advanced Capabilities in GOMA 6.0 - Augmenting Conditions Automatic Continuation and Linear Stability Analysis. Office of Scientific and Technical Information (OSTI), February 2015. http://dx.doi.org/10.2172/1490545.

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Miner, Kimberley, and Robin Rodgers. Parts unmapped : linear multi-variate analysis of food, water, and temperature requirements for regional stability. Environmental Research and Development Program (U.S.), April 2019. http://dx.doi.org/10.21079/11681/32565.

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Manzini, Gianmarco, Hashem Mohamed Mourad, Paola Francesca Antonietti, Italo Mazzieri, and Marco Verani. The arbitrary-order virtual element method for linear elastodynamics models. Convergence, stability and dispersion-dissipation analysis. Office of Scientific and Technical Information (OSTI), May 2020. http://dx.doi.org/10.2172/1630838.

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Goldberg, Moshe, and Marvin Marcus. Stability Analysis of Finite Difference Schemes for Hyperbolic Systems and Problems in Applied and Computational Linear Algebra. Fort Belvoir, VA: Defense Technical Information Center, July 1988. http://dx.doi.org/10.21236/ada201083.

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Marcus, Marvin, and Moshe Goldberg. Stability Analysis of Finite Difference Schemes for Hyperbolic Systems, and Problems in Applied and Computational Linear Algebra. Fort Belvoir, VA: Defense Technical Information Center, August 1985. http://dx.doi.org/10.21236/ada161092.

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Altstein, Miriam, and Ronald J. Nachman. Rational Design of Insect Control Agent Prototypes Based on Pyrokinin/PBAN Neuropeptide Antagonists. United States Department of Agriculture, August 2013. http://dx.doi.org/10.32747/2013.7593398.bard.

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The general objective of this study was to develop rationally designed mimetic antagonists (and agonists) of the PK/PBAN Np class with enhanced bio-stability and bioavailability as prototypes for effective and environmentally friendly pest insect management agents. The PK/PBAN family is a multifunctional group of Nps that mediates key functions in insects (sex pheromone biosynthesis, cuticular melanization, myotropic activity, diapause and pupal development) and is, therefore, of high scientific and applied interest. The objectives of the current study were: (i) to identify an antagonist biophores (ii) to develop an arsenal of amphiphilic topically active PK/PBAN antagonists with an array of different time-release profiles based on the previously developed prototype analog; (iii) to develop rationally designed non-peptide SMLs based on the antagonist biophore determined in (i) and evaluate them in cloned receptor microplate binding assays and by pheromonotropic, melanotropic and pupariation in vivo assays. (iv) to clone PK/PBAN receptors (PK/PBAN-Rs) for further understanding of receptor-ligand interactions; (v) to develop microplate binding assays for screening the above SMLs. In the course of the granting period A series of amphiphilic PK/PBAN analogs based on a linear lead antagonist from the previous BARD grant was synthesized that incorporated a diverse array of hydrophobic groups (HR-Suc-A[dF]PRLa). Others were synthesized via the attachment of polyethylene glycol (PEG) polymers. A hydrophobic, biostablePK/PBAN/DH analog DH-2Abf-K prevented the onset of the protective state of diapause in H. zea pupae [EC50=7 pmol/larva] following injection into the preceding larval stage. It effectively induces the crop pest to commit a form of ‘ecological suicide’. Evaluation of a set of amphiphilic PK analogs with a diverse array of hydrophobic groups of the formula HR-Suc-FTPRLa led to the identification of analog T-63 (HR=Decyl) that increased the extent of diapause termination by a factor of 70% when applied topically to newly emerged pupae. Another biostablePK analog PK-Oic-1 featured anti-feedant and aphicidal properties that matched the potency of some commercial aphicides. Native PK showed no significant activity. The aphicidal effects were blocked by a new PEGylated PK antagonist analog PK-dF-PEG4, suggesting that the activity is mediated by a PK/PBAN receptor and therefore indicative of a novel and selective mode-of-action. Using a novel transPro mimetic motif (dihydroimidazole; ‘Jones’) developed in previous BARD-sponsored work, the first antagonist for the diapause hormone (DH), DH-Jo, was developed and shown to block over 50% of H. zea pupal diapause termination activity of native DH. This novel antagonist development strategy may be applicable to other invertebrate and vertebrate hormones that feature a transPro in the active core. The research identifies a critical component of the antagonist biophore for this PK/PBAN receptor subtype, i.e. a trans-oriented Pro. Additional work led to the molecular cloning and functional characterization of the DH receptor from H. zea, allowing for the discovery of three other DH antagonist analogs: Drosophila ETH, a β-AA analog, and a dF analog. The receptor experiments identified an agonist (DH-2Abf-dA) with a maximal response greater than native DH. ‘Deconvolution’ of a rationally-designed nonpeptide heterocyclic combinatorial library with a cyclic bis-guanidino (BG) scaffold led to discovery of several members that elicited activity in a pupariation acceleration assay, and one that also showed activity in an H. zea diapause termination assay, eliciting a maximal response of 90%. Molecular cloning and functional characterization of a CAP2b antidiuretic receptor from the kissing bug (R. prolixus) as well as the first CAP2b and PK receptors from a tick was also achieved. Notably, the PK/PBAN-like receptor from the cattle fever tick is unique among known PK/PBAN and CAP2b receptors in that it can interact with both ligand types, providing further evidence for an evolutionary relationship between these two NP families. In the course of the granting period we also managed to clone the PK/PBAN-R of H. peltigera, to express it and the S. littoralis-R Sf-9 cells and to evaluate their interaction with a variety of PK/PBAN ligands. In addition, three functional microplate assays in a HTS format have been developed: a cell-membrane competitive ligand binding assay; a Ca flux assay and a whole cell cAMP ELISA. The Ca flux assay has been used for receptor characterization due to its extremely high sensitivity. Computer homology studies were carried out to predict both receptor’s SAR and based on this analysis 8 mutants have been generated. The bioavailability of small linear antagonistic peptides has been evaluated and was found to be highly effective as sex pheromone biosynthesis inhibitors. The activity of 11 new amphiphilic analogs has also been evaluated. Unfortunately, due to a problem with the Heliothis moth colony we were unable to select those with pheromonotropic antagonistic activity and further check their bioavailability. Six peptides exhibited some melanotropic antagonistic activity but due to the low inhibitory effect the peptides were not further tested for bioavailability in S. littoralis larvae. Despite the fact that no new antagonistic peptides were discovered in the course of this granting period the results contribute to a better understanding of the interaction of the PK/PBAN family of Nps with their receptors, provided several HT assays for screening of libraries of various origin for presence of PK/PBAN-Ragonists and antagonists and provided important practical information for the further design of new, peptide-based insecticide prototypes aimed at the disruption of key neuroendocrine physiological functions in pest insects.
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