ADAPTIVE FINITE ELEMENT TECHNIQUES FOR THE ACOUSTIC WAVE EQUATION

2001 ◽  
Vol 09 (02) ◽  
pp. 575-591 ◽  
Author(s):  
WOLFGANG BANGERTH ◽  
ROLF RANNACHER

We present an adaptive finite element method for solving the acoustic wave equation. Using a global duality argument and Galerkin orthogonality, we derive an identity for the error with respect to an arbitrary functional output of the solution. The error identity is evaluated by solving the dual problem numerically. The resulting local cell-wise error indicators are used in the grid adaptation process. In this way, the space-time mesh can be tailored for the efficient computation of the quantity of interest. We give an overview of the implementation of the proposed method and illustrate its performance by several numerical examples.

Geophysics ◽  
1991 ◽  
Vol 56 (12) ◽  
pp. 2114-2117 ◽  
Author(s):  
Christopher L. Liner

The theory of 2.5-dimensional (2.5-D) wave propagation (Bleistein, 1986) allows efficient computation of 3-D wavefields in c(x, z) acoustic media when the source and receivers lie in a common y-plane (assumed to be y = 0 in this paper). It is really a method of efficiently computing an inplane 3-D wavefield in media with one symmetry axis. The idea is to raytrace the wavefield in the (x, z)-plane while allowing for out‐of‐plane spreading. In this way 3-D amplitude decay is honored without 3-D ray tracing. This theory has its conceptual origin in work by Ursin (1978) and Hubral (1978). Bleistein (1986) gives an excellent overview and detailed reference to earlier work.


2011 ◽  
Vol 3 (1) ◽  
pp. 181-203 ◽  
Author(s):  
Samir Karaa

AbstractIn this paper, we investigate the stability and convergence of a family of implicit finite difference schemes in time and Galerkin finite element methods in space for the numerical solution of the acoustic wave equation. The schemes cover the classical explicit second-order leapfrog scheme and the fourth-order accurate scheme in time obtained by the modified equation method. We derive general stability conditions for the family of implicit schemes covering some well-known CFL conditions. Optimal error estimates are obtained. For sufficiently smooth solutions, we demonstrate that the maximal error in the L2-norm error over a finite time interval converges optimally as O(hp+1 + ∆ts), where p denotes the polynomial degree, s=2 or 4, h the mesh size, and ∆t the time step.


2006 ◽  
Vol 16 (04) ◽  
pp. 587-614 ◽  
Author(s):  
P. MASSIMI ◽  
A. QUARTERONI ◽  
G. SCROFANI

Various types of oil traps have been found to be associated with salt domes in subsurface geology. In this paper the diapiric rise of light salt layers through a denser overburden — the surrounding rocks — is modeled assuming that, in a geological time scale, salt and rocks layers behave like Newtonian fluids. A Lagrangian approach is adopted to track the interface between layers, within the framework of a finite element space discretization. An accurate description of large deformations due to salt movement is achieved using a grid adaptation technique based on geometrical refinement. Different geological cases have been simulated in order to describe the behavior of rocks and estimate the effect on diapiric growth of buoyancy force, differential loading, gravitational gliding and thin-skinned regional extension. Our computational model accounts also for sedimentation and compaction of the overburden.


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