Mode-filtering analysis of space and time harmonic wave components of magnetic fields in rotating machinery

2010 ◽  
Vol 172 (2) ◽  
pp. 55-63
Author(s):  
Kenji Miyata ◽  
Kazumasa Ide ◽  
Kazuo Shima
Keyword(s):  
Magnetic Fields ◽  
Harmonic Wave ◽  
Rotating Machinery ◽  
Space And Time ◽  
Time Harmonic

Topological sensitivity analysis revisited for time-harmonic wave scattering problems. Part I: the free space case

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Frédérique Le Louër ◽  
María-Luisa Rapún
Keyword(s):  
Free Space ◽  
Order Term ◽  
Harmonic Wave ◽  
Dirichlet Condition ◽  
Point Sources ◽  
Neumann Condition ◽  
Scattering Problems ◽  
Content Type ◽  
Time Harmonic ◽  
Topological Gradient

PurposeIn this paper, the authors revisit the computation of closed-form expressions of the topological indicator function for a one step imaging algorithm of two- and three-dimensional sound-soft (Dirichlet condition), sound-hard (Neumann condition) and isotropic inclusions (transmission conditions) in the free space.Design/methodology/approachFrom the addition theorem for translated harmonics, explicit expressions of the scattered waves by infinitesimal circular (and spherical) holes subject to an incident plane wave or a compactly supported distribution of point sources are available. Then the authors derive the first-order term in the asymptotic expansion of the Dirichlet and Neumann traces and their surface derivatives on the boundary of the singular medium perturbation.FindingsAs the shape gradient of shape functionals are expressed in terms of boundary integrals involving the boundary traces of the state and the associated adjoint field, then the topological gradient formulae follow readily.Originality/valueThe authors exhibit singular perturbation asymptotics that can be reused in the derivation of the topological gradient function that generates initial guesses in the iterated numerical solution of any shape optimization problem or imaging problems relying on time-harmonic acoustic wave propagation.

ACCURATE FINITE DIFFERENCE REPRESENTATION OF NEUMANN BOUNDARY DATA FOR TIME-HARMONIC WAVE PROPAGATION

1996 ◽  
Vol 04 (04) ◽  
pp. 425-432 ◽  
Author(s):  
ISAAC HARARI
Keyword(s):  
Finite Difference ◽  
Boundary Data ◽  
Truncation Error ◽  
Harmonic Wave ◽  
Neumann Boundary ◽  
Local Truncation Error ◽  
Matrix Equations ◽  
Order Accuracy ◽  
Time Harmonic ◽  
Global Accuracy

Finite difference stencils for inhomogeneous Neumann boundary conditions in acoustic problems with arbitrary source distributions are constructed and analyzed. Boundary stencils are compatible with corresponding interior stencils, preserving symmetry of matrix equations without degrading global accuracy. Higher-order accuracy is attained within the compact support of lower-order methods. Results are verified by local truncation error analysis.

A note on diffraction by a right-angled wedge

1965 ◽  
Vol 61 (1) ◽  
pp. 275-278 ◽  
Author(s):  
W. E. Williams
Keyword(s):  
Wave Function ◽  
Wave Equation ◽  
Surface Wave ◽  
Harmonic Wave ◽  
Boundary Value ◽  
Normal Derivative ◽  
Support Surface ◽  
Closed Form Solutions ◽  
Time Harmonic

It has been shown in recent years ((5)–(8), (10)) that it is possible to obtain closed form solutions for the time harmonic wave equation when a linear combination of the wave function and its normal derivative is prescribed on the surface of a wedge. Boundary-value problems of this type occur in the problem of diffraction by a highly conducting wedge or by a wedge whose surfaces are thinly coated with dielectric. In certain circumstances such surfaces can support surface waves and one important aspect of the solution of the boundary-value problem is the determination of the amplitude of the surface wave excited.

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