Modeling of static magnetic anomaly created by iron plates

Abstract

Abstract-This paper deals with the modeling of thin steel shells placed in a static magnetic field. The variable used is the scalar reduced potential. In front of the diversity of the formulations encountered, it proposes a methodological approach of different methods and compares them, in term of speed and easiness of computation.Index Terms-Boundary integral method, finite elements method, magnetostatic, thin shell.

Ships Magnetic Anomaly Computation With Integral Equation and Fast Multipole Method

“…This reversible permeability corresponds to small and linear variations of the magnetization when the material underlies such low fields. Considering that (3) and combining it with (1) and (2), we get the expression of the induced magnetization (4) where is the field created by the whole magnetized shell and can be expressed with an integral equation. Combining this equation with (4), we obtain the classical integral volume equation for magnetostatic linear problem [8].…”

“…Another difficulty is the very high ratio between the length of the ship and the thickness of the hull which leads to an unacceptable number of elements if the hull is meshed in its volume. Of course, this situation can be avoided if surface elements, modelling the special magnetic behavior of the sheet, are used [4]. The last but not the least is to model degaussing coils effects.…”

How to well pose a magnetization identification problem

“…If we consider that (4) and (5) we obtain as div Equation (7) is equivalent to Poisson's equation; the magnetization of the shell can then be considered as equivalent to a distribution of charges located on S. Thus, the relation between this distribution and the tangential magnetization is We notice that the charge distribution is a mathematical abstraction but represents the flux of induction entering the shell form the air region [4]. The advantage of (3) and (9) is their validity everywhere in the air region (i.e., outboard and onboard the device).…”

An Accelerated 3D-Magnetostatic Field Computation Method With Tetrahedral Surface Integrals

“…Due to the complex geometric features of vehicles, numerical methods, such as the finite element method (FEM) [8], the boundary element method (BEM) [9] and the integral equation method (IEM) [10,11] have been effective tools for calculating the induced magnetism accurately. IEM may be more suitable for open-boundary magnetostatic field calculations that avoid meshing the air region (or the equivalent) [10][11][12][13].…”

“…To overcome the disadvantages described above, accelerated approaches, such as ACA [15], FMM [11,16] and the parallel computing method [17], have been applied to successfully realize large-scale magnetism computations. The ACA, FMM, and the parallel computing technique for IEM method are three independent methods (the parallel computing method can also be intergrated with the ACA or the FMM) for accelerating the magnetostatic field computation, and the memory cost can also be reduced by the three methods simultaneously.…”