Fictitious wave domain modelling and analysis of marine CSEM data

2019 ◽  
Vol 219 (1) ◽  
pp. 223-238
Author(s):  
Jie Lu ◽  
Yuguo Li ◽  
Zhijun Du
Keyword(s):  
Boundary Condition ◽  
Wave Propagation ◽  
Frequency Domain ◽  
Time Domain ◽  
Sea Water ◽  
High Order ◽  
Water Model ◽  
Complex Frequency ◽  
Novel Approach ◽  
Marine Csem

SUMMARY Modelling marine controlled-source electromagnetic (CSEM) responses in the fictitious time domain is a novel approach, which facilitates the full exploration of EM diffusive properties in the fictitious wave domain (FWD). Concepts, such as reflections, refractions, diffractions and transmissions, which are used for the analysis of elastic wave propagation can thus be adopted in FWD for interpreting CSEM data. In this paper, we use a high-order finite difference time domain (FDTD) algorithm for modelling marine CSEM responses in both the fictitious time domain and the diffusive frequency domain. A complex frequency shifted perfectly matched layer (CFS–PML) boundary condition is adopted to the FDTD modelling. We demonstrate the performance of the CFS–PML boundary condition and validate the high-order FDTD code in the FWD with the half-space sea water model and in the frequency domain with the 1-D canonical reservoir model. We investigate and analyse the propagation characteristics of electromagnetic fields in the FWD, where we apply wave propagation concepts to interpret marine CSEM data. Similarities between wave and field propagations relevant for marine CSEM data are demonstrated through several 1-D to 3-D numerical examples.

A NONLINEAR PLANE-WAVE ALGORITHM FOR DIFFRACTIVE PROPAGATION INVOLVING SHOCKWAVES

1993 ◽  
Vol 01 (03) ◽  
pp. 371-393 ◽  
Author(s):  
P. TED CHRISTOPHER
Keyword(s):  
Wave Propagation ◽  
Plane Wave ◽  
Frequency Domain ◽  
Time Domain ◽  
Burgers Equation ◽  
Propagation Model ◽  
Nonlinear Beam ◽  
Nonlinear Plane ◽  
Very High ◽  
Plane Wave Propagation

A new algorithm for nonlinear plane-wave propagation is presented. The algorithm uses a novel time domain representation to account for nonlinearity, while accounting for absorption in the frequency domain. The new algorithm allows for accurate representations of diffractive shockwave propagation in the framework of an existing nonlinear beam propagation model using far fewer harmonics (and thus time) than alternative algorithms based on a frequency domain solution to Burgers' equation. The new algorithm is tested against the frequency domain solution to Burgers' equation in a variety of cases and then used to model a focused ultrasonic piston transducer operating at very high source intensities.

2.5-D modeling of seismic wave propagation: Boundary condition, stability criterion, and efficiency

Geophysics ◽  
1998 ◽  
Vol 63 (6) ◽  
pp. 2082-2090 ◽  
Author(s):  
Shunhua Cao ◽  
Stewart Greenhalgh
Keyword(s):  
Boundary Condition ◽  
Wave Propagation ◽  
Boundary Conditions ◽  
Traveling Waves ◽  
Time Domain ◽  
Stability Criterion ◽  
Spatial Location ◽  
Seismic Wave Propagation ◽  
Sampling Scheme ◽  
Maximum Value

The modeling of 3-D wave propagation in media having only 2-D variation in the elastic properties—so‐called 2.5-D modeling—is achieved using the wavenumber transform, in which multiple 2-D problems are solved, each one associated with a different strike‐direction wavenumber [Formula: see text] We derived a 2.5-D transmitting boundary condition in the frequency domain, which has no simple representation in the time domain. It yields significantly improved results over existing boundary conditions. For time‐domain methods, attenuating boundary conditions must be applied. The 2.5-D stability criterion changes from the 2-D to the 3-D criterion as the wavenumber increases from zero to the maximum value for traveling waves, respectively. In the frequency‐wavenumber ([Formula: see text]) domain at a given spatial location, the wavefield for a fixed frequency (ω) oscillates at progressively higher rates as wavenumber ([Formula: see text]) increases from zero to the maximum value for traveling waves. A nonuniform sampling scheme in wavenumber space, to exploit the oscillatory nature of the wavefield, yields significant efficiency improvement over the normal uniform sampling scheme.

A Complex Frequency Domain Model of Wind Turbine Structures

1995 ◽  
Vol 117 (4) ◽  
pp. 311-317 ◽  
Author(s):  
P. So̸rensen ◽  
G. C. Larsen ◽  
C. J. Christensen
Keyword(s):  
Wind Turbine ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Model ◽  
Horizontal Axis ◽  
Complex Frequency ◽  
Horizontal Axis Wind Turbine ◽  
The Time Domain

The present paper describes a frequency domain model of the structure of an operating horizontal axis wind turbine with three or more blades. The frequency domain model is implemented along with an analogous time domain model in a PC code. This PC code is used to verify the frequency domain model comparing loads on the structure calculated with the frequency domain model both to loads calculated with the time domain model and to measured loads.

scholarly journals Frequency-domain elastic wavefield simulation with hybrid absorbing boundary conditions

2019 ◽  
Vol 16 (4) ◽  
pp. 690-706
Author(s):  
Zhencong Zhao ◽  
Jingyi Chen ◽  
Xiaobo Liu ◽  
Baorui Chen
Keyword(s):  
Boundary Condition ◽  
Free Surface ◽  
Boundary Conditions ◽  
Frequency Domain ◽  
Time Domain ◽  
Absorbing Boundary Conditions ◽  
Elastic Media ◽  
Absorbing Boundary ◽  
Wavefield Simulation ◽  
The Time Domain

Abstract The frequency-domain seismic modeling has advantages over the time-domain modeling, including the efficient implementation of multiple sources and straightforward extension for adding attenuation factors. One of the most persistent challenges in the frequency domain as well as in the time domain is how to effectively suppress the unwanted seismic reflections from the truncated boundaries of the model. Here, we propose a 2D frequency-domain finite-difference wavefield simulation in elastic media with hybrid absorbing boundary conditions, which combine the perfectly matched layer (PML) boundary condition with the Clayton absorbing boundary conditions (first and second orders). The PML boundary condition is implemented in the damping zones of the model, while the Clayton absorbing boundary conditions are applied to the outer boundaries of the damping zones. To improve the absorbing performance of the hybrid absorbing boundary conditions in the frequency domain, we apply the complex coordinate stretching method to the spatial partial derivatives in the Clayton absorbing boundary conditions. To testify the validity of our proposed algorithm, we compare the calculated seismograms with an analytical solution. Numerical tests show the hybrid absorbing boundary condition (PML plus the stretched second-order Clayton absorbing condition) has the best absorbing performance over the other absorbing boundary conditions. In the model tests, we also successfully apply the complex coordinate stretching method to the free surface boundary condition when simulating seismic wave propagation in elastic media with a free surface.

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