A Nonlinear Dynamics Analysis of Vortex-Structure Interaction Models

2001 ◽  
Vol 123 (4) ◽  
pp. 475-479 ◽  
Author(s):  
N. W. Mureithi ◽  
S. Goda ◽  
H. Kanki ◽  
T. Nakamura
Keyword(s):  
Nonlinear Dynamics ◽  
Parameter Space ◽  
Vortex Structure ◽  
Three Dimensional ◽  
Order Model ◽  
Third Order ◽  
Interaction Models ◽  
Structure Interaction ◽  
Lock In ◽  
Fifth Order

Vortex-structure interaction models are studied in the work presented here. The third- order model by Hartlen and Currie (HC model) can reproduce the correct response amplitude, while a fifth-order model by Landl predicts the observed hysterisis effect. Using concepts from nonlinear dynamics and bifurcation theory, the range of possible dynamics of the models is investigated in parameter space; essentially, a class of nonlinear oscillators deriving “naturally” from the HC model is studied. It is found that perturbations of the HC model in parameter space lead to qualitatively physically meaningful dynamics. Forced excitation of the HC model is the highlight of the work. In this case, it is shown that a subharmonic lock-in predicted by the model may be related to a three-dimensional secondary subharmonic instability of a periodic flow. Experimental results are presented for comparison.

scholarly journals Design and Analysis of a Repetitive Current Controller for a Single-Phase Bridgeless SEPIC PFC Converter

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 131 ◽  
Author(s):  
Jinwoo Kim ◽  
Sanghun Han ◽  
Wontae Cho ◽  
Younghoon Cho ◽  
Hyunsoo Koh
Keyword(s):  
Controller Design ◽  
Harmonic Distortion ◽  
Input Current ◽  
Order Model ◽  
Third Order ◽  
Current Controller ◽  
The Stability ◽  
Small Signal Modeling ◽  
Fifth Order ◽  
Repetitive Controller

This paper studies a repetitive controller design scheme for a bridgeless single-ended primary inductor converter (SEPIC) power factor correction (PFC) converter to mitigate input current distortions. A small signal modeling of the converter is performed by a fifth-order model. Since the fifth-order model is complex to be applied in designing a current controller, the model is approximated to a third-order model. Using the third-order model, the repetitive controller is designed to reduce the input current distortion. Then, the stability of the repetitive controller is verified with an error transfer function. The proposed controller performance is validated by simulation, and the experiment results show that the input current total harmonic distortion (THD) is improved by applying the proposed controller for an 800 W bridgeless SEPIC PFC converter prototype.

Characterizing the Two- and Three-Dimensional Resolution of an Improved Aberration-Corrected STEM

2009 ◽  
Vol 15 (5) ◽  
pp. 441-453 ◽  
Author(s):  
A.R. Lupini ◽  
A.Y. Borisevich ◽  
J.C. Idrobo ◽  
H.M. Christen ◽  
M. Biegalski ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Scanning Transmission Electron Microscope ◽  
Third Order ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Microscopes ◽  
Dopant Atoms ◽  
Fifth Order ◽  
Initial Results ◽  
Aberration Corrected

AbstractThe successful development of third-order aberration correctors in transmission electron microscopy has seen aberration-corrected electron microscopes evolve from specialist projects, custom built at a small number of sites to common instruments in many modern laboratories. Here we describe some initial results illustrating the two- and three-dimensional (3D) performance of an aberration-corrected scanning transmission electron microscope with a prototype improved aberration corrector designed to also minimize fifth-order aberrations and a new, higher brightness gun. We show that atomic columns separated by 0.63 Å can be resolved and demonstrate detection of single dopant atoms with 3D sensitivity.

scholarly journals Modulated anharmonic ADPs are intrinsic to aperiodic crystals: a case study on incommensurate Rb2ZnCl4

2011 ◽  
Vol 67 (3) ◽  
pp. 205-217 ◽  
Author(s):  
Liang Li ◽  
Alexander Wölfel ◽  
Andreas Schönleber ◽  
Swastik Mondal ◽  
Antoine M. M. Schreurs ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Atomic Displacement ◽  
Quantitative Information ◽  
Third Order ◽  
Modulated Structures ◽  
Incommensurate Modulation ◽  
Atomic Displacement Parameters ◽  
Difference Fourier ◽  
Lock In ◽  
Fifth Order

A combination of structure refinements, analysis of the superspace MEM density and interpretation of difference-Fourier maps has been used to characterize the incommensurate modulation of rubidium tetrachlorozincate, Rb2ZnCl4, at a temperature of T = 196 K, close to the lock-in transition at T lock-in = 192 K. The modulation is found to consist of a combination of displacement modulation functions, modulated atomic displacement parameters (ADPs) and modulated third-order anharmonic ADPs. Up to fifth-order Fourier coefficients could be refined against diffraction data containing up to fifth-order satellite reflections. The center-of-charge of the atomic basins of the MEM density and the displacive modulation functions of the structure model provide equivalent descriptions of the displacive modulation. Modulations of the ADPs and anharmonic ADPs are visible in the MEM density, but extracting quantitative information about these modulations appears to be difficult. In the structure refinements the modulation parameters of the ADPs form a dependent set, and ad hoc restrictions had to be introduced in the refinements. It is suggested that modulated harmonic ADPs and modulated third-order anharmonic ADPs form an intrinsic part, however small, of incommensurately modulated structures in general. Refinements of alternate models with and without parameters for modulated ADPs lead to significant differences between the parameters of the displacement modulation in these two types of models, thus showing the modulation of ADPs to be important for a correct description of the displacive modulation. The resulting functions do not provide evidence for an interpretation of the modulation by a soliton model.

scholarly journals Triality and the consistent reductions on AdS3 × S3

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Camille Eloy ◽  
Gabriel Larios ◽  
Henning Samtleben
Keyword(s):  
Field Theory ◽  
Nonlinear Dynamics ◽  
Parameter Space ◽  
Three Dimensional ◽  
Parameter Family ◽  
Duality Group ◽  
Consistent Truncations ◽  
Two Parameter ◽  
Kaluza Klein

Abstract We study compactifications on AdS3×S3 and deformations thereof. We exploit the triality symmetry of the underlying duality group SO(4,4) of three-dimensional supergravity in order to construct and relate new consistent truncations. For non-chiral D = 6, $$ \mathcal{N} $$ N 6d = (1, 1) supergravity, we find two different consistent truncations to three-dimensional supergravity, retaining different subsets of Kaluza-Klein modes, thereby offering access to different subsectors of the full nonlinear dynamics. As an application, we construct a two-parameter family of AdS3 × M3 backgrounds on squashed spheres preserving U(1)2 isometries. For generic value of the parameters, these solutions break all supersymmetries, yet they remain perturbatively stable within a non-vanishing region in parameter space. They also contain a one-parameter family of $$ \mathcal{N} $$ N = (0, 4) supersymmetric AdS3 × M3 backgrounds on squashed spheres with U(2) isometries. Using techniques from exceptional field theory, we determine the full Kaluza-Klein spectrum around these backgrounds.

scholarly journals Fluid–structure interaction in a fully coupled three-dimensional mitral–atrium–pulmonary model

2021 ◽  
Author(s):  
Liuyang Feng ◽  
Hao Gao ◽  
Nan Qi ◽  
Mark Danton ◽  
Nicholas A. Hill ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Left Atrium ◽  
Left Atrial ◽  
Left Atrial Appendage ◽  
Pulmonary Veins ◽  
Three Dimensional ◽  
Left Heart ◽  
Structure Interaction ◽  
Acute Mitral Regurgitation ◽  
Reversal Flow

AbstractThis paper aims to investigate detailed mechanical interactions between the pulmonary haemodynamics and left heart function in pathophysiological situations (e.g. atrial fibrillation and acute mitral regurgitation). This is achieved by developing a complex computational framework for a coupled pulmonary circulation, left atrium and mitral valve model. The left atrium and mitral valve are modelled with physiologically realistic three-dimensional geometries, fibre-reinforced hyperelastic materials and fluid–structure interaction, and the pulmonary vessels are modelled as one-dimensional network ended with structured trees, with specified vessel geometries and wall material properties. This new coupled model reveals some interesting results which could be of diagnostic values. For example, the wave propagation through the pulmonary vasculature can lead to different arrival times for the second systolic flow wave (S2 wave) among the pulmonary veins, forming vortex rings inside the left atrium. In the case of acute mitral regurgitation, the left atrium experiences an increased energy dissipation and pressure elevation. The pulmonary veins can experience increased wave intensities, reversal flow during systole and increased early-diastolic flow wave (D wave), which in turn causes an additional flow wave across the mitral valve (L wave), as well as a reversal flow at the left atrial appendage orifice. In the case of atrial fibrillation, we show that the loss of active contraction is associated with a slower flow inside the left atrial appendage and disappearances of the late-diastole atrial reversal wave (AR wave) and the first systolic wave (S1 wave) in pulmonary veins. The haemodynamic changes along the pulmonary vessel trees on different scales from microscopic vessels to the main pulmonary artery can all be captured in this model. The work promises a potential in quantifying disease progression and medical treatments of various pulmonary diseases such as the pulmonary hypertension due to a left heart dysfunction.

Modeling of aortic valve stenosis using fluid-structure interaction method

Perfusion ◽  
2021 ◽  
pp. 026765912199854
Author(s):  
Mohammad Javad Ghasemi Pour ◽  
Kamran Hassani ◽  
Morteza Khayat ◽  
Shahram Etemadi Haghighi
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Relaxation Phase ◽  
Exercise Condition ◽  
Time Dependent Domain ◽  
Comparison Of The Results

Background and objectives: Fluid structure interaction (FSI) is defined as interaction of the structures with contacting fluids. The aortic valve experiences the interaction with blood flow in systolic phase. In this study, we have tried to predict the hemodynamics of blood flow through a normal and stenotic aortic valve in two relaxation and exercise conditions using a three-dimensional FSI method. Methods: The aorta valve was modeled as a three-dimensional geometry including a normal model and two others with 25% and 50% stenosis. The geometry of the aortic valve was extracted from CT images and the models were generated by MMIMCS software and then they were implemented in ANSYS software. The pulsatile flow rate was used for all cases and the numerical simulations were conducted based on a time-dependent domain. Results: The obtained results including the velocity, pressure, and shear stress contours in different systolic time sequences were explained and discussed. The maximum blood flow velocity in relaxation phase was obtained 1.62 m/s (normal valve), 3.78 m/s (25% stenosed valve), and 4.73 m/s (50% stenosed valve). In exercise condition, the maximum velocities are 2.86, 4.32, and 5.42 m/s respectively. The maximum blood pressure in relaxation phase was calculated 111.45 mmHg (normal), 148.66 mmHg (25% stenosed), and 164.21 mmHg (50% stenosed). However, the calculated values in exercise situation were 129.57, 163.58, and 191.26 mmHg. The validation of the predicted results was also conducted using existing literature. Conclusions: We believe that such model are useful tools for biomechanical experts. The further studies should be done using experimental data and the data are implemented on the boundary conditions for better comparison of the results.

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