scholarly journals Acoustic and inertial modes in planetary-like rotating ellipsoids

2020 ◽  
Vol 476 (2239) ◽  
pp. 20200131
Author(s):  
Jérémie Vidal ◽  
David Cébron
Keyword(s):  
Finite Element ◽  
Liquid Core ◽  
Normal Modes ◽  
Flow Dynamics ◽  
Rotating Fluid ◽  
Rotating Fluids ◽  
Dynamical Models ◽  
Planetary Interiors ◽  
Physical Insight ◽  
Insight Into

The bounded oscillations of rotating fluid-filled ellipsoids can provide physical insight into the flow dynamics of deformed planetary interiors. The inertial modes, sustained by the Coriolis force, are ubiquitous in rapidly rotating fluids and Vantieghem (2014, Proc. R. Soc. A , 470 , 20140093. doi:10.1098/rspa.2014.0093 ) pioneered a method to compute them in incompressible fluid ellipsoids. Yet, taking density (and pressure) variations into account is required for accurate planetary applications, which has hitherto been largely overlooked in ellipsoidal models. To go beyond the incompressible theory, we present a Galerkin method in rigid coreless ellipsoids, based on a global polynomial description. We apply the method to investigate the normal modes of fully compressible, rotating and diffusionless fluids. We consider an idealized model, which fairly reproduces the density variations in the Earth’s liquid core and Jupiter-like gaseous planets. We successfully benchmark the results against standard finite-element computations. Notably, we find that the quasi-geostrophic inertial modes can be significantly modified by compressibility, even in moderately compressible interiors. Finally, we discuss the use of the normal modes to build reduced dynamical models of planetary flows.

On the Vibration of a Nearly Cyclic System

1996 ◽  
Vol 210 (3) ◽  
pp. 267-275
Author(s):  
G F Wu ◽  
X J Liu
Keyword(s):  
Weak Coupling ◽  
Solution Method ◽  
Structural Model ◽  
Normal Modes ◽  
Vibration Modes ◽  
Effective Solution ◽  
Physical Insight ◽  
New Perspective ◽  
Component Assembly ◽  
Insight Into

In this paper, the vibration modes of the structural model of a nearly cyclic multiply mono-coupled multi-degree-of-freedom (multi-DOF) component assembly are examined. The attention is focused on the mode similarity phenomenon among the vibration deformation shapes of all the components for the disordered assemblies with relatively weak coupling. By means of this particular characteristic of the normal modes of such a system, an effective solution method based on the analysis of a single component system is developed, which can be used to find any specified structural frequency within any given frequency band and its corresponding mode of the system directly. This solution scheme, in a new perspective, provides a direct physical insight into the relation between the imperfection effects and the various structural and imperfection parameters. Numerical examples are given at the end.

A Locally Modal B-Spline Based Full-Vector Finite-Element Method with PML for Nonlinear and Lossy Plasmonic Waveguide

Frequenz ◽  
2016 ◽  
Vol 70 (9-10) ◽  
Author(s):  
Hossein Karimi ◽  
Saeid Nikmehr ◽  
Ehsan Khodapanah
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Beam Propagation Method ◽  
Beam Propagation ◽  
Nonlinear Modes ◽  
B Spline ◽  
Spline Finite Element ◽  
Physical Insight ◽  
Insight Into ◽  
Element Method

AbstractIn this paper, we develop a B-spline finite-element method (FEM) based on a locally modal wave propagation with anisotropic perfectly matched layers (PMLs), for the first time, to simulate nonlinear and lossy plasmonic waveguides. Conventional approaches like beam propagation method, inherently omit the wave spectrum and do not provide physical insight into nonlinear modes especially in the plasmonic applications, where nonlinear modes are constructed by linear modes with very close propagation constant quantities. Our locally modal B-spline finite element method (LMBS-FEM) does not suffer from the weakness of the conventional approaches. To validate our method, first, propagation of wave for various kinds of linear, nonlinear, lossless and lossy materials of metal-insulator plasmonic structures are simulated using LMBS-FEM in MATLAB and the comparisons are made with FEM-BPM module of COMSOL Multiphysics simulator and B-spline finite-element finite-difference wide angle beam propagation method (BSFEFD-WABPM). The comparisons show that not only our developed numerical approach is computationally more accurate and efficient than conventional approaches but also it provides physical insight into the nonlinear nature of the propagation modes.

Simulation and Control of Two Side Direction Burr

2011 ◽  
Vol 143-144 ◽  
pp. 428-432 ◽  
Author(s):  
Hai Jun Qu ◽  
J.H. Yang ◽  
Gui Cheng Wang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Formation Mechanism ◽  
Element Model ◽  
Burr Formation ◽  
Analysis Method ◽  
Physical Insight ◽  
Side Face ◽  
And Control ◽  
Insight Into

A finite element model was developed for simulation of two side direction burr formation process. Based on strain distribution, a two side burr formation mechanism was proposed. Burr form and burr size of simulation are close to that's of experiment. Finite element model generated here provided a numerical analysis method to solve the prediction of burr and chip formation and physical insight into the fundamental burr formation mechanism. The stain in two side direction of material near the side face decides the shape and the size of two side direction. Multi-workpieces are machined at the same time with side face closely by each others can control the formation of two side direction strain and two side direction burr.

scholarly journals Intrinsic DMI-free skyrmion formation and robust dynamic behaviors in magnetic hemispherical shells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jaehak Yang ◽  
Claas Abert ◽  
Dieter Suess ◽  
Sang-Koog Kim
Keyword(s):  
Finite Element ◽  
Dynamic Properties ◽  
Perpendicular Magnetic Anisotropy ◽  
Micromagnetic Simulations ◽  
Out Of Plane ◽  
Physical Insight ◽  
Planar Geometries ◽  
Hemispherical Shells ◽  
Moriya Interaction ◽  
Insight Into

AbstractWe performed finite-element micromagnetic simulations to examine the formation of skyrmions without intrinsic Dzyaloshinskii–Moriya interaction (DMI) in magnetic hemispherical shells. We found that curvature-induced DM-like interaction allows for further stabilization of skyrmions without the DMI in curved-geometry hemispherical shells for a specific range of uniaxial perpendicular magnetic anisotropy (PMA) constant Ku. The larger the curvature of the shell, the higher the Ku value required for the formation of the skyrmions. With well-stabilized skyrmions, we also found in-plane gyration modes and azimuthal spin-wave modes as well as an out-of-plane breathing mode, similarly to previously found modes for planar geometries. Furthermore, additional higher-frequency hybrid modes were observed due to coupling between the gyration and azimuthal modes. This work provides further physical insight into the static and dynamic properties of intrinsic DMI-free skyrmions formed in curved-geometry systems.

Analysis of the Feed Direction Burr in Turning Based on FEM

2011 ◽  
Vol 268-270 ◽  
pp. 1222-1227
Author(s):  
Hai Jun Qu ◽  
Gui Cheng Wang ◽  
Yun Ming Zhu ◽  
X.D. Zhu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Formation Mechanism ◽  
Element Model ◽  
Burr Formation ◽  
Analysis Method ◽  
Progressive Change ◽  
Feed Direction ◽  
Physical Insight ◽  
Insight Into

A finite element model was developed for simulation of feed direction burr formation process in turning. Based on a series of stress and strain contours the progressive change of geometry at the edge of workpiece edge from simulation, a turning feed direction burr formation mechanism is proposed and divided into four stages: normal cutting stage, deformation of workpiece edge stage, continues cutting stage and final developed stage. The removal of the remaining part of allowance takes place close to the tool tip as the material has sufficient rigidity to allow cutting only in this area in final developed stage and secondary burr will be formed; primary burr will be formed in final developed stage if the remaining material has no rigidity to allow cutting continually in final developed stage. The burr size and burr shapes form simulation results are consistent with the experimental results. Finite element model generated here provided a numerical analysis method to solve the prediction of burr formation and physical insight into the fundamental burr formation mechanism.

scholarly journals A New Method for Field-Balancing of High-Speed Flexible Rotors without Trial Weights

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Y. A. Khulief ◽  
M. A. Mohiuddin ◽  
M. El-Gebeily
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
High Speed ◽  
Flexible Rotor ◽  
Analytical Technique ◽  
Flexible Rotors ◽  
Physical Insight ◽  
Benchmark Solutions ◽  
Rotor Balancing ◽  
Insight Into

Flexible rotor balancing, in general, relies to a great extent on physical insight into the modal nature of the unbalance response. The objective of this investigation is to develop a hybrid experimental/analytical technique for balancing high-speed flexible rotors. The developed technique adopts an approach that combines the finite element modeling, experimental modal analysis, vibration measurements, and mathematical identification. The modal imbalances are identified and then transformed to the nodal space, in order to determine a set of physical balancing masses at some selected correction planes. The developed method does not rely on trial runs. In addition, the method does not require operating the supercritical rotor in a high-speed balancing facility, while accounting for the contribution of higher significant modes. The developed scheme is applied to a multidisk, multibearing, high-speed flexible rotor, where the interaction between the rotor-bending operating deflections and the forces resulting from the residual unbalance are appreciable. Some new benchmark solutions and observations are reported. The applicability, reliability, and challenges that may be encountered in field applications are addressed.

scholarly journals Design of a Novel Miniaturized Frequency Selective Surface Based on 2.5-Dimensional Jerusalem Cross for 5G Applications

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Peng Zhao ◽  
Yihang Zhang ◽  
Rongrong Sun ◽  
Wen-Sheng Zhao ◽  
Yue Hu ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Equivalent Circuit ◽  
Equivalent Circuit Model ◽  
Frequency Selective Surface ◽  
Size Reduction ◽  
Two Dimensional ◽  
Physical Insight ◽  
Frequency Selective ◽  
Significant Size ◽  
Insight Into

A compact frequency selective surface (FSS) for 5G applications has been designed based on 2.5-dimensional Jerusalem cross. The proposed element consists of two main parts: the successive segments of the metal traces placed alternately on the two surfaces of the substrate and the vertical vias connecting traces. Compared with previous published two-dimensional miniaturized elements, the transmission curves indicate a significant size reduction (1/26 wavelengths at the resonant frequency) and exhibit good angular and polarization stabilities. Furthermore, a general equivalent circuit model is established to provide direct physical insight into the operating principle of this FSS. A prototype of the proposed FSS has been fabricated and measured, and the results validate this design.

Endwall Blockage in Axial Compressors

1999 ◽  
Vol 121 (3) ◽  
pp. 499-509 ◽  
Author(s):  
S. A. Khalid ◽  
A. S. Khalsa ◽  
I. A. Waitz ◽  
C. S. Tan ◽  
E. M. Greitzer ◽  
...  
Keyword(s):  
Tip Clearance ◽  
Design Parameters ◽  
Tip Clearance Flow ◽  
Axial Compressors ◽  
Clearance Flow ◽  
Flow Features ◽  
Physical Insight ◽  
Level Loading ◽  
Stagger Angle ◽  
Insight Into

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.

Three Turnaround Heat Treating Studies

2003 ◽  
Author(s):  
Jaan Taagepera ◽  
Marty Clift ◽  
D. Mike DeHart ◽  
Keneth Marden
Keyword(s):  
Heat Treatment ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Heat Treating ◽  
Element Analysis ◽  
Stress Profiles ◽  
Insight Into

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.

scholarly journals Gravitational wave–gauge field dynamics

2017 ◽  
Vol 26 (12) ◽  
pp. 1742005 ◽  
Author(s):  
R. R. Caldwell ◽  
C. Devulder ◽  
N. A. Maksimova
Keyword(s):  
Quantum Gravity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gauge Field ◽  
Linear Combination ◽  
Effective Mass ◽  
Normal Modes ◽  
New Approaches ◽  
Insight Into

The dynamics of a gravitational wave propagating through a cosmic gauge field are dramatically different than in vacuum. We show that a gravitational wave acquires an effective mass, is birefringent, and its normal modes are a linear combination of gravitational waves and gauge field excitations, leading to the phenomenon of gravitational wave–gauge field oscillations. These surprising results provide an insight into gravitational phenomena and may suggest new approaches to a theory of quantum gravity.

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