Direct Simulation of Scattering and Absorption by Particle Deposits

2006 ◽  
Author(s):  
Daniel W. Mackowski
Keyword(s):  
Large Scale ◽  
Incident Beam ◽  
Amplitude Distribution ◽  
Addition Theorem ◽  
Spherical Particles ◽  
Direct Simulation ◽  
Vector Spherical Harmonic ◽  
Linearly Polarized ◽  
Scattered Fields ◽  
Radiative Absorption

A computational scheme is presented to exactly calculate the electromagnetic field distribution, and associated radiative absorption and scattering characteristics, of large-scale ensembles of spherical particles that are subjected to a focussed incident beam. The method employs a superposition extension to Lorenz/Mie theory, in which the internal and scattered fields for each sphere in the ensemble are represented by vector spherical harmonic expansions, and boundary conditions at the surfaces of the spheres are matched by application of the addition theorem for vector harmonics. The incident field is modeled as a transverse, linearly-polarized wave with a Gaussian amplitude distribution along a fixed focal plane. Application of the method to prediction of the absorption and reflectance characteristics of particle deposits is discussed, and illustrative calculations are presented.

Analytic solutions of the scattering by two multilayered dielectric spheres

1992 ◽  
Vol 70 (9) ◽  
pp. 696-705 ◽  
Author(s):  
A-K. Hamid ◽  
I. R. Ciric ◽  
M. Hamid
Keyword(s):  
Boundary Conditions ◽  
Cross Sections ◽  
Plane Electromagnetic Wave ◽  
Expansion Method ◽  
Analytic Solutions ◽  
Addition Theorem ◽  
Modal Expansion ◽  
Modal Expansion Method ◽  
Dielectric Spheres ◽  
Scattered Fields

The problem of plane electromagnetic wave scattering by two concentrically layered dielectric spheres is investigated analytically using the modal expansion method. Two different solutions to this problem are obtained. In the first solution the boundary conditions are satisfied simultaneously at all spherical interfaces, while in the second solution an iterative approach is used and the boundary conditions are satisfied successively for each iteration. To impose the boundary conditions at the outer surface of the spheres, the translation addition theorem of the spherical vector wave functions is employed to express the scattered fields by one sphere in the coordiante system of the other sphere. Numerical results for the bistatic and back-scattering cross sections are presented graphically for various sphere sizes, layer thicknesses and permittivities, and angles of incidence.

Polarization analysis in magnetic x‐ray scattering using 45° linearly polarized x‐ray incident beam (abstract)

1992 ◽  
Vol 63 (1) ◽  
pp. 1176-1176
Author(s):  
Koichi Mori ◽  
Kazumichi Namikawa ◽  
Yoshisato Funahashi ◽  
Yasuo Higashi ◽  
Masami Ando
Keyword(s):  
Incident Beam ◽  
Polarization Analysis ◽  
X Ray ◽  
X Ray Scattering ◽  
Linearly Polarized ◽  
Ray Scattering

scholarly journals The Magnetized Disk-Halo Transition Region of M51

2018 ◽  
Vol 14 (A30) ◽  
pp. 319-322 ◽  
Author(s):  
M. Kierdorf ◽  
S. A. Mao ◽  
A. Fletcher ◽  
R. Beck ◽  
M. Haverkorn ◽  
...  
Keyword(s):  
Transition Region ◽  
Large Scale ◽  
Model Parameters ◽  
Very Large Array ◽  
X Band ◽  
Model Predictions ◽  
The Galaxy ◽  
Linearly Polarized ◽  
Grand Design ◽  
Different Depths

AbstractAn excellent laboratory for studying large scale magnetic fields is the grand design face-on spiral galaxy M51. Due to wavelength-dependent Faraday depolarization, linearly polarized synchrotron emission at different radio frequencies gives a picture of the galaxy at different depths: Observations at L-band (1 – 2 GHz) probe the halo region while at C- and X-band (4 – 8 GHz) the linearly polarized emission probe the disk region of M51. We present new observations of M51 using the Karl G. Jansky Very Large Array (VLA) at S-band (2 – 4 GHz), where previously no polarization observations existed, to shed new light on the transition region between the disk and the halo. We discuss a model of the depolarization of synchrotron radiation in a multilayer magneto-ionic medium and compare the model predictions to the multi-frequency polarization data of M51 between 1 – 8 GHz. The new S-band data are essential to distinguish between different models. Our study shows that the initial model parameters, i.e. the total regular and turbulent magnetic field strengths in the disk and halo of M51, need to be adjusted to successfully fit the models to the data.

scholarly journals Plasmonic interference modulation for broadband nanofocusing

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shaobo Li ◽  
Shuming Yang ◽  
Fei Wang ◽  
Qiang Liu ◽  
Biyao Cheng ◽  
...  
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Incident Beam ◽  
Plasmonic Mode ◽  
Resonant Structures ◽  
Interference Modulation ◽  
Near Field Imaging ◽  
Linearly Polarized ◽  
Radially Polarized

Abstract Metallic plasmonic probes have been successfully applied in near-field imaging, nanolithography, and Raman enhanced spectroscopy because of their ability to squeeze light into nanoscale and provide significant electric field enhancement. Most of these probes rely on nanometric alignment of incident beam and resonant structures with limited spectral bandwidth. This paper proposes and experimentally demonstrates an asymmetric fiber tip for broadband interference nanofocusing within its full optical wavelengths (500–800 nm) at the nanotip with 10 nm apex. The asymmetric geometry consisting of two semicircular slits rotates plasmonic polarization and converts the linearly polarized plasmonic mode to the radially polarized plasmonic mode when the linearly polarized beam couples to the optical fiber. The three-dimensional plasmonic modulation induces circumference interference and nanofocus of surface plasmons, which is significantly different from the nanofocusing through plasmon propagation and plasmon evolution. The plasmonic interference modulation provides fundamental insights into the plasmon engineering and has important applications in plasmon nanophotonic technologies.

Direct Simulation of Electrorheological Suspensions

2001 ◽  
Author(s):  
Aijun Wang ◽  
Pushpendra Singh ◽  
Nadine Aubry
Keyword(s):  
Electric Field ◽  
Stokes Equations ◽  
Hydrodynamic Force ◽  
Particle System ◽  
Electrostatic Force ◽  
Body Motion ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Point Dipole ◽  
Direct Simulation

Abstract A new distributed multiplier/fictitious (DLM) domain method is developed for direct simulation of electrorheological (ER) suspensions subjected to spatially uniform electrical fields. The method is implemented both in two and three dimensions. The fluid-particle system is treated implicitly using the combined weak formulation described in [1,2]. The governing Navier-Stokes equations for the fluid are solved everywhere, including the interior of the particles. The flow inside the particles is forced to be a rigid body motion by a distribution of Lagrange multipliers. The electrostatic force acting on the polarized spherical particles is modeled based on the point-dipole approximation. Using our code we have studied the time evolution of particle-scale structures of ER suspensions in channels subjected to the pressure driven flow. In our study, the flow direction is perpendicular to that of the electric field. Simulations show that when the hydrodynamic force is zero, or very small compared to the electrostatic force, the particles form chains that are aligned approximately parallel to the direction of electric field. But, when the magnitude of hydrodynamic force is comparable to that of the electrostatic force the particle chains orient at an angle with the direction of the electric field. The angle between the particle chain and the direction of the electric field depends on the relative strengths of the hydrodynamic and electrostatic forces.

Scattering of a Gaussian beam by an anisotropic-coated eccentric conducting circular cylinder

2020 ◽  
Vol 12 (9) ◽  
pp. 900-905
Author(s):  
Shi-Chun Mao ◽  
Zhen-Sen Wu ◽  
Zhaohui Zhang ◽  
Jiansen Gao ◽  
Lijuan Yang
Keyword(s):  
Gaussian Beam ◽  
Plane Waves ◽  
Approximate Expression ◽  
Transverse Magnetic ◽  
Addition Theorem ◽  
Electric Polarization ◽  
Electric Conductor ◽  
Solution Convergence ◽  
Local Coordinates ◽  
Scattered Fields

AbstractA solution to the problem of Gaussian beam scattering by a circular perfect electric conductor coated with eccentrically anisotropic media is presented. The incident Gaussian beam source is expanded as an approximate expression in the simple form with Taylor's series. The transmitted field in the anisotropically coated region is expressed as an infinite summation of Eigen plane waves with different polar angles. The unknown coefficients of the scattered fields are obtained with the aid of the boundary conditions. The addition theorem for cylindrical functions is applied to transfer from the local coordinates to the global ones. The infinite series can be truncated under the prerequisite of achieving the solution convergence. Only the case of transverse-electric polarization is discussed. The similar formulation of transverse-magnetic polarization can be obtained by adopting a similar method. Some numerical results are presented and discussed. The result is in agreement with that available as expected when the eccentric geometry comes to the concentric one.

scholarly journals Direct numerical simulation of the oscillatory flow around a sphere resting on a rough bottom

2017 ◽  
Vol 822 ◽  
pp. 235-266 ◽  
Author(s):  
Marco Mazzuoli ◽  
Paolo Blondeaux ◽  
Julian Simeonov ◽  
Joseph Calantoni
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Coarse Sand ◽  
Spherical Particles ◽  
Navier Stokes ◽  
Sea Waves ◽  
Spherical Object ◽  
Navier Stokes Equations

The oscillatory flow around a spherical object lying on a rough bottom is investigated by means of direct numerical simulations of the continuity and Navier–Stokes equations. The rough bottom is simulated by a layer/multiple layers of spherical particles, the size of which is much smaller that the size of the object. The period and amplitude of the velocity oscillations of the free stream are chosen to mimic the flow at the bottom of sea waves and the size of the small spherical particles falls in the range of coarse sand/very fine gravel. Even though the computational costs allow only the simulation of moderate values of the Reynolds number characterizing the bottom boundary layer, the results show that the coherent vortex structures, shed by the spherical object, can break up and generate turbulence, if the Reynolds number of the object is sufficiently large. The knowledge of the velocity field allows the dynamics of the large-scale coherent vortices shed by the object to be determined and turbulence characteristics to be evaluated. Moreover, the forces and torques acting on both the large spherical object and the small particles, simulating sediment grains, can be determined and analysed, thus laying the groundwork for the investigation of sediment dynamics and scour developments.

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

2018 ◽  
Vol 25 (3) ◽  
pp. 748-756 ◽  
Author(s):  
M. X. Tang ◽  
Y. Y. Zhang ◽  
J. C. E ◽  
S. N. Luo
Keyword(s):  
Single Crystal ◽  
Large Scale ◽  
Incident Beam ◽  
Wave Structure ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Case Transmission ◽  
Dynamics Simulations

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

Sign in / Sign up

Export Citation Format

Share Document