The Shadow Boundary Integral for the Reduction of Truncation Error in Near-Field to Far-Field Transformations

2005 ◽  
Author(s):  
L. Infante ◽  
E. Martini ◽  
A. Peluso ◽  
S. Maci
Keyword(s):  
Truncation Error ◽  
Near Field ◽  
Boundary Integral ◽  
Far Field ◽  
Shadow Boundary

scholarly journals Spectral boundary integral method for simulating static and dynamic fields from a fault rupture in a poroelastodynamic solid

2021 ◽  
Author(s):  
Elias Heimisson ◽  
Antonio Pio Rinaldi
Keyword(s):  
Pore Pressure ◽  
Integral Method ◽  
Near Field ◽  
Boundary Integral ◽  
Pressure Response ◽  
Boundary Integral Method ◽  
P Wave ◽  
Computational Time ◽  
Far Field ◽  
Pore Pressure Response

The spectral boundary integral method is popular for simulating fault, fracture, and frictional processes at a planar interface. However, the method is less commonly used to simulate off-fault dynamic fields. Here we develop a spectral boundary integral method for poroelastodynamic solid. The method has two steps: first, a numerical approximation of a convolution kernel and second, an efficient temporal convolution of slip speed and the appropriate kernel. The first step is computationally expensive but easily parallelizable and scalable such that the computational time is mostly restricted by computational resources. The kernel is independent of the slip history such that the same kernel can be used to explore a wide range of slip scenarios. We apply the method by exploring the short-time dynamic and static responses: first, with a simple source at intermediate and far-field distances and second, with a complex near-field source. We check if similar results can be attained with dynamic elasticity and undrained pore-pressure response and conclude that such an approach works well in the near-field but not necessarily at an intermediate and far-field distance. We analyze the dynamic pore-pressure response and find that the P-wave arrival carries a significant pore pressure peak that may be observed in high sampling rate pore-pressure measurements. We conclude that a spectral boundary integral method may offer a viable alternative to other approaches where the bulk is discretized, providing a better understanding of the near-field dynamics of the bulk in response to finite fault ruptures.

scholarly journals A new strategy to reduce the truncation error in near-field/far-field transformations

Radio Science ◽  
2000 ◽  
Vol 35 (1) ◽  
pp. 3-17 ◽  
Author(s):  
O. M. Bucci ◽  
G. D'Elia ◽  
M. D. Migliore
Keyword(s):  
Truncation Error ◽  
Near Field ◽  
Far Field ◽  
New Strategy

scholarly journals AN EFFECTIVE TECHNIQUE FOR REDUCING THE TRUNCATION ERROR IN THE NEAR-FIELD-FAR-FIELD TRANSFORMATION WITH PLANE-POLAR SCANNING

2007 ◽  
Vol 73 ◽  
pp. 213-238 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Giovanni Riccio
Keyword(s):  
Truncation Error ◽  
Near Field ◽  
Far Field ◽  
Effective Technique ◽  
Field Transformation

Boundary-Integral Representation of Linear Free-Surface Potential Flows

1997 ◽  
Vol 41 (01) ◽  
pp. 10-16
Author(s):  
Francis Noblesse ◽  
Chi Yang ◽  
Xiao-Bo Chen
Keyword(s):  
Velocity Field ◽  
Potential Flow ◽  
Near Field ◽  
Boundary Surface ◽  
Flow Region ◽  
Numerical Differentiation ◽  
Boundary Integral ◽  
Diffraction Radiation ◽  
Linear Potential ◽  
Far Field

A new potential-flow representation, which defines the velocity field ∇ϕ in a potential flow region explicitly in terms of the velocity distribution (u,v,w) at a boundary surface E, is given for the case of wave diffraction-radiation by a ship. This flow representation does not involve the potential ϕ at ϵ (unlike the usual Green identity which expresses ϕ within a flow domain in terms of boundary values of ϕ and ∂ϕ/∂n) and defines the velocity field ∇ϕ directly (i.e., not via numerical differentiation of ϕ). The new flow representation can be useful for extending a given near-field flow into the far field, and for coupling a near-field nonlinear viscous flow calculation method and a far-field linear potential-flow representation.

Near Field Expression of Ship Wave Resistance by Green’s Theorem

2016 ◽  
Author(s):  
Takashi Tsubogo
Keyword(s):  
Integral Equation ◽  
Near Field ◽  
Field Method ◽  
Momentum Conservation ◽  
Wave Resistance ◽  
Boundary Integral ◽  
Far Field ◽  
Ship Wave ◽  
Direct Pressure ◽  
Run Up

The ship wave resistance can be estimated by two alternative methods after solving the boundary integral equation. One is the far field method e.g. Havelock’s formula based on momentum conservation in fluid domain, and another is the near field method based on direct pressure integration over the wetted body surface. Nakos and Sclavounos (1994) had shown a new near field expression of ship wave resistance from the momentum conservation law in the fluid domain with linearized free surface condition. Their new expression differs slightly from the traditional near field form. This problem of near field expression is reconsidered in terms of Green’s second identity. After linearization of the free suface condition and some transformation of equations, the present paper will agree with the Nakos and Sclavounos’ near field expression for the ship wave resistance. Some numerical calculations of wave resistance from the far field method and from the near field method are shown using the classical Kelvin sources distributed on the centerplane of thin ship but solving the different boundary integral equation. Numerical results suggest that the problematic run-up square integration along the waterline is to be omitted as a higher order small quantity. If this run-up term is omitted in each method except for far field, the traditional direct pressure integrtaion is equal to the Nakos and Sclavounos’ near field expression.

scholarly journals Fast computation of electromagnetic near-fields with the multilevel fast multipole method combining near-field and far-field translations

2006 ◽  
Vol 4 ◽  
pp. 111-115 ◽  
Author(s):  
A. Tzoulis ◽  
T. F. Eibert
Keyword(s):  
Electromagnetic Compatibility ◽  
Fast Multipole Method ◽  
Near Field ◽  
Boundary Integral ◽  
Far Field ◽  
Discrete Elements ◽  
Fast Multipole ◽  
Equivalent Current ◽  
Multipole Method ◽  
Current Densities

Abstract. In Electromagnetic Compatibility (EMC) problems, computation of electromagnetic near-fields in the vicinity of complex radiation and scattering systems is often required. Numerical solution of such problems is achieved using Boundary Integral (BI) based approaches, where the involved Integral Equations (IE's) are solved with the Method of Moments (MoM). The MoM solution process is speeded up by fast IE solvers such as the Multilevel Fast Multipole Method (MLFMM). In the end the desired amplitudes of the expansion of the equivalent current densities on the discrete elements all over the Huygens' surfaces are known. Computation of the electromagnetic fields produced by the equivalent currents at observation points being in the near-field regions requires integration of the current densities over the Huygens' surfaces. Numerical evaluation of the near-field integrals using conventional integration rules can become extremely time consuming for large objects and large number of observation points. In this contribution, acceleration of the near-field integration of the equivalent current densities is provided using a postprocessing MLFMM, where near-field and far-field translations are combined in order to achieve optimum performance. The proposed approach was applied in the postprocessing stage of a powerful Finite Element Boundary Element (FEBI) method, resulting in significant decrease of the postprocessing computation time. The formulation of the proposed acceleration is presented and numerical results are shown.

Magnetic Tag Antenna for UHF Near-field and Far-Field RFID Applications

2015 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
Mondher Dhaouadi ◽  
M. Mabrouk ◽  
T. Vuong ◽  
A. Ghazel
Keyword(s):  
Near Field ◽  
Far Field ◽  
Rfid Applications
Sign in / Sign up

Export Citation Format

Share Document