Non-deteriorating time domain numerical algorithms for Maxwell's electrodynamics

作者：Petropavlovsky S; Tsynkov S^*

来源：Journal of Computational Physics, 2017, 336: 1-35.

DOI：10.1016/j.jcp.2017.01.068

• Unsteady electromagnetic waves
• Maxwell's equations
• Unbounded regions
• Grid truncation
• Artificial outer boundaries
• Artificial boundary conditions (ABCs)
• Non-reflecting boundaries
• Perfectly matched layer (PML)
• Long time deterioration
• Loss of accuracy, loss of stability, error build-up
• The Huygens' principle
• Aft fronts of the waves
• Lacunae of the solutions
• Quasi-lacunae
• Accumulation of charge
• Guaranteed accuracy
• Temporally uniform error bounds

The Huygens' principle and lacunae can help construct efficient far-field closures for the numerical simulation of unsteady waves propagating over unbounded regions. Those closures can be either standalone or combined with other techniques for the treatment of artificial outer boundaries. A standalone lacunae-based closure can be thought of as a special artificial boundary condition (ABC) that is provably free from any error associated with the domain truncation. If combined with a different type of ABC or a perfectly matched layer (PML), a lacunae-based approach can help remove any long-time deterioration (e.g., instability) that arises at the outer boundary regardless of why it occurs in the first place.
A specific difficulty associated with Maxwell's equations of electromagnetism is that in general their solutions do not have classical lacunae and rather have quasi-lacunae. Unlike in the classical case, the field inside the quasi-lacunae is not zero; instead, there is an electrostatic solution driven by the electric charges that accumulate over time. In our previous work [23], we have shown that quasi-lacunae can also be used for building the far-field closures. However, for achieving a provably non-deteriorating performance over arbitrarily long time intervals, the accumulated charges need to be known ahead of time. The main contribution of the current paper is that we remove this limitation and modify the algorithm in such a way that one can rather avoid the accumulation of charge all together. Accordingly, the field inside the quasi-lacunae becomes equal to zero, which facilitates obtaining the temporally uniform error estimates as in the case of classical lacunae. The performance of the modified algorithm is corroborated by a series of numerical simulations. The range of problems that the new method can address includes important combined formulations, for which the interior subproblem may be non Huygens', and only the exterior subproblem, i.e., the far field, is Huygens'.

• 出版日期2017-5-1