scholarly journals Babich's expansion and the fast Huygens sweeping method for the Helmholtz wave equation at high frequencies

2016 ◽  
Vol 313 ◽  
pp. 478-510 ◽  
Author(s):  
Wangtao Lu ◽  
Jianliang Qian ◽  
Robert Burridge
Keyword(s):  
Wave Equation ◽  
High Frequencies ◽  
Sweeping Method ◽  
Helmholtz Wave Equation

scholarly journals On the parabolic equation method for water-wave propagation

1979 ◽  
Vol 95 (1) ◽  
pp. 159-176 ◽  
Author(s):  
A. C. Radder
Keyword(s):  
Wave Equation ◽  
Water Wave ◽  
Asymptotic Form ◽  
Incident Plane Wave ◽  
Parabolic Approximation ◽  
Periodic Surface ◽  
High Frequencies ◽  
Contour Lines ◽  
Incident Plane ◽  
Bottom Contour

A parabolic approximation to the reduced wave equation is investigated for the propagation of periodic surface waves in shoaling water. The approximation is derived from splitting the wave field into transmitted and reflected components.In the case of an area with straight and parallel bottom contour lines, the asymptotic form of the solution for high frequencies is compared with the geometrical optics approximation.Two numerical solution techniques are applied to the propagation of an incident plane wave over a circular shoal.

Asymptotic formula for the capacitance of two oppositely charged discs

1981 ◽  
Vol 89 (2) ◽  
pp. 373-384 ◽  
Author(s):  
W. C Chew ◽  
J. A Kong
Keyword(s):  
Wave Equation ◽  
Integral Equations ◽  
Total Charge ◽  
Two Dimensional ◽  
Dimensional Problem ◽  
Dual Integral Equations ◽  
Asymptotic Formulae ◽  
Parallel Strips ◽  
Helmholtz Wave Equation ◽  
Oppositely Charged

AbstractAsymptotic formulae for the capacitances of two oppositely charged, identical, circular, coaxial discs and two identical, infinite parallel strips separated by dielectric slabs are derived from the dual integral equations approach. The formulation in terms of dual integral equations using transforms gives rise to relatively simple Green's functions in the transformed space and renders the derivation of the asymptotic formulae relatively easy. The solution near the edge of the plates, a two-dimensional problem previously thought not solvable by the Wiener-Hopf technique, is solved indirectly using the method. Solution of the Helmholtz wave equation is first sought, and the solution to Laplace's equation is obtained by letting the wavenumber go to zero. The solution away from the edge is obtained by solving the dual integral equations approximately. The total charge on the plate is obtained by matching the solution near the edge and away from the edge giving the capacitance.

Inverse Scattering Solutions by a Sinc Basis, Multiple Source, Moment Method -- Part III: Fast Algorithms

1984 ◽  
Vol 6 (1) ◽  
pp. 103-116
Author(s):  
S. A. Johnson ◽  
Y. Zhou ◽  
M. K. Tracy ◽  
M. J. Berggren ◽  
F. Stenger
Keyword(s):  
Wave Equation ◽  
Inverse Scattering ◽  
Scattering Problem ◽  
Inverse Scattering Problem ◽  
Algebraic Equations ◽  
The Past ◽  
Nonlinear Algebraic Equations ◽  
Detector Geometry ◽  
Scattering Potential ◽  
Helmholtz Wave Equation

Solving the inverse scattering problem for the Helmholtz wave equation without employing the Born or Rytov approximations is a challenging problem, but some slow iterative methods have been proposed. One such method suggested by us is based on solving systems of nonlinear algebraic equations that are derived by applying the method of moments to a sinc basis function expansion of the fields and scattering potential. In the past, we have solved these equations for a 2-D object of n by n pixels in a time proportional to n5. In the present paper, we demonstrate a new method based on FFT convolution and the concept of backprojection which solves these equations in time proportional to n3 • log(n). Several numerical examples are given for images up to 7 by 7 pixels in size. Analogous algorithms to solve the Riccati wave equation in n3 • log(n) time are also suggested, but not verified. A method is suggested for interpolating measurements from one detector geometry to a new perturbed detector geometry whose measurement points fall on a FFT accessible, rectangular grid and thereby render many detector geometrics compatible for use by our fast methods.

scholarly journals Alternative derivations for the fields inside a waveguide

2021 ◽  
Vol 72 (2) ◽  
pp. 129-131
Author(s):  
Raghavendra G. Kulkarni
Keyword(s):  
Magnetic Field ◽  
Wave Equation ◽  
Electric Field ◽  
Longitudinal Magnetic Field ◽  
Transverse Electric ◽  
Transverse Magnetic ◽  
Longitudinal Electric Field ◽  
Microwave Engineering ◽  
Introductory Textbooks ◽  
Helmholtz Wave Equation

Abstract Generally, the longitudinal magnetic field of the transverse electric (TE) wave inside a waveguide is obtained by solving the corresponding Helmholtz wave equation, which further leads to the derivation of the remaining fields. In this paper, we provide an alternative way to obtain this longitudinal magnetic field by making use of one of the Maxwell’s equations instead of directly relying on the Helmholtz wave equation. The longitudinal electric field of the transverse magnetic (TM) wave inside a waveguide can also be derived in a similar fashion. These derivations, which are different from those found in the introductory textbooks on microwave engineering, make the study of waveguides more interesting.

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