Application of perfectly matched layers to the transient modeling of subsurface EM problems

Berenger's perfectly matched layers (PML) have been found to be very efficient as a material absorbing boundary condition (ABC) for finite-difference time-domain (FDTD) modeling of lossless media. In this paper, we apply the PML technique to truncate the simulation region of conductive media. Examples are given to show some possible applications of the PML technique to subsurface problems with lossy media. To apply the PML ABC for lossy media, we first modify the original 3-D Maxwell's equations to achieve PML at the boundaries of the simulation region. The modified equations are then solved by using a staggered grid with a central-differencing scheme. A 3-D FDTD code has been written on the basis of our PML formulation to simulate the electromagnetic field responses of a dipole source in both lossless and lossy media. The code is first tested against analytical solutions for homogeneous media of different losses and then applied to some subsurface problems, such as a geological fault and a buried gas tank. Very interesting propagation and scattering phenomena are observed ifom the simulation results. Some analyses are also given to explain the physical phenomena of the calculated waveforms.link_to_subscribed_fulltex

Perfectly matched layer and piecewise-linear recursive convolution for the FDTD solution of the 3D dispersive half-space problem

A 3D unite-difference time-domain simulation of a dispersive, inhomogeneous half-space problem is described. The formulation uses the perfectly matched layer (PML) absorbing boundary condition (ABC) extended to dispersive media. The dispersion is characterized by a two-species Debye model with parameters taken from reported experimental data of soils with different moisture contents. The time-stepping scheme for the electric field uses the piecewise-linear recursive convolution (PLRC) method. For homogeneous half-space problems, the simulation results are compared against results from numerical integration of Sommerfeld-type integrals. To illustrate its applications, the inhomogeneous half-space simulations include results from the ground penetrating radar simulated response of buried objects in realistic soils. © 1998 IEEE.link_to_subscribed_fulltex

3D PML-FDTD simulation of ground penetrating radar on dispersive earth media

A 3D finite-difference time-domain simulation of ground penetrating radar (GPR) is described. The soil material is characterized by inhomogeneities, conductive loss and strong dispersion. The dispersion is modelled by a N-th order Lorentz model and implemented by recursive convolution. The Perfectly Matched Layer (PML) is used as an absorbing boundary condition (ABC). This formulation facilitates the parallelization of the code. A code is written for a 32 processor system. Almost linear speedup is observed. Results include the radargrams of buried objects.link_to_subscribed_fulltex

Parallel 3D PML-FDTD simulation of GPR on dispersive, inhomogeneous and conductive media

A 3D FDTD simulation of ground penetrating radar (GPR) is described. The soil material is characterized by inhomogeneities, conductive loss and strong dispersion. The dispersion is modelled by a N-th order Lorentz model and implemented by recursive convolution. The perfectly matched layer (PML) Is used as an absorbing boundary condition (ABC). This formulation facilitates the parallelization of the code. A code is written for a 32 processor system. Almost linear speedup is observed. Results include the radargrams of buried objects.link_to_subscribed_fulltex

Finite-difference time-domain simulation of ground penetrating radar on dispersive, inhomogeneous, and conductive soils

A three-dimensional (3-D) time-domain numerical scheme for simulation of ground penetrating radar (GPR) on dispersive and inhomogeneous soils with conductive loss is described. The finite-difference time-domain (FDTD) method is used to discretize the partial differential equations for time stepping of the electromagnetic fields. The soil dispersion is modeled by multiterm Lorentz and/or Debye models and incorporated into the FDTD scheme by using the piecewise-linear recursive convolution (PLRC) technique. The dispersive soil parameters are obtained by fitting the model to reported experimental data. The perfectly matched layer (PML) is extended to match dispersive media and used as an absorbing boundary condition to simulate an open space. Examples are given to verify the numerical solution and demonstrate its applications. The 3-D PML-PLRC-FDTD formulation facilitates the parallelization of the code. A version of the code is written for a 32-processor system, and an almost linear speedup is observed. © 1998 IEEE.link_to_subscribed_fulltex