A non-overlapping Schwarz domain decomposition method with high-order finite elements for flow acoustics

A non-overlapping and non-conformal domain decomposition method (DDM) is presented for modelling large finite antenna arrays. There are two major ingredients in the proposed DDM: (a) A new second-order transmission condition is introduced, which improves convergence of the iterative process. In contrast to previous high order interface conditions, the new condition uses two second-order transverse derivatives to address the slow convergence issue of both TE and TM evanescent modes. Numerical experiments demonstrate that the convergence of the proposed algorithm is quite insensitive to the size of array. (b) The proposed non-conformal DDM not only permits the use of completely independent discretization for each of the sub-domains, but also allows adjacent sub-domains to be geometrically non-conformal. The benefits of the non-conformal nature of the proposed DDM will be fully enjoyed by a large-scale problem of practical interest, which is a 50 by 50 ultra wide band (UWB) array in the presence of a slot frequency selective surface (FSS). Numerical results verify the effectiveness of the proposed method.

A posteriori error analysis for two non-overlapping domain decomposition techniques

Fast estimation of discretization error for FE problems solved by domain decomposition

A non-overlapping domain decomposition method with non-matching grids for modeling large finite antenna arrays

In this paper, we are concerned with the non-overlapping domain decomposition method with non-matching grids for three-dimensional elliptic equations. For this method, the interface variable is chosen as the mortar multiplier. We first develop a class of inexact solvers for the interface Poincare-Steklov operator associated with such a domain decomposition. Then we use the inexact solver to construct a new preconditioner for the interface problem arising from the Finite Element Tearing and Interconnecting method. It will be shown that the condition number of the preconditioned system grows only as the logarithm of the dimension of the local problem associated with an individual substructure, and is independent of possible jumps of the coefficient in the elliptic equation.

Advances in interconnect technologies, such as the increase of the number of metal layers and 3-D stacking technique, have paved the way for higher functionality and superior performance while reducing size, power, and cost in today's integrated circuits and package products. With the increase of clock frequency and edge rates as well as the continuously downscaling of feature size and 3-D interconnect technologies in high-speed systems, signal integrity (SI) effects such as signal delay, reflection, attenuation, dispersion and crosstalk have become one of the dominant factors in current deep sub-micrometer CMOS technologies limiting overall performance of high-speed systems.Another major difficulty is the power integrity (PI) issue. For example, IR drop is caused by the finite resistivity (R) of metals and current (I) drawn off from the power/ground planes. Chip designs are susceptible to IR drop, especially when the integrated circuit (IC) supply voltage Vdd decreases with the scaling of silicon processes. IR drop is proportional to the resistance of the power/ground plane. When the resistance of power/ground plane increases, with the shrinking of complex geometries, the IR drops will in turn increase as well. To further confound the difficult issue, the rise of the thermal temperature due to the current carrying interconnects also has tremendous impact on the IC performance and reliability. Current flow in a VLSI interconnect can cause a power dissipation, which is referred to as Joule heating or self-heating. The Joule heating effects are becoming increasingly significant with the shrinking scale of silicon process because of the increase of on-chip power density, inclusion of more metal layers with higher densities, and the use of dielectric materials with lower thermal conductivities. Subsequently, the temperature effects on the electrical performance of 3D systems should be carefully considered as well in the electrical designs.Unfortunately, almost all practical SI and PI problems are multi-physics in nature, and various physical phenomena are usually interacting and coupling to each other. For instance, the resistivity of most conducting metals increases linearly with the increases of the surrounding temperature resulting from the Joule heating by electric currents flowing through the conductors. Therefore, in order to accurately characterize the performance of high power integrated circuits (ICs), packages and printed circuit boards (PCBs), it is essential to account for both electric and thermal effects and the intimate couplings between them.In this paper, we propose to use non-conformal, non-overlapping domain decomposition methods (DDMs) for the signal integrity analyses and thermal-aware DC IR drop co-analysis of high-power IC-Package-PCBs. The proposed DDM starts by partitioning the composite device into inhomogeneous sub-regions with temperature dependent material properties. Subsequently, each sub-domain is meshed independently according to its own characteristic features. As a result, the troublesome mesh generation task for complex ICs can be greatly subdued. Moreover, the proposed thermal-aware DC IR drop co-analysis applies the non-conformal DDMs for both conduction and steady state heat transfer analyses with a two-way coupling between them. Furthermore, we extend the non-conformal DDM to study transient thermal temperature distribution within complex ICs. Numerical examples, including an IC package and an IC-Package-PCB, demonstrate the flexibility and potentials of the proposed non-conformal DDMs for SI analyses and thermal-aware DC IR-drop co-analysis.

In this article, a nonconformal and nonoverlapping domain decomposition method (DDM) based on surface integral equation (SIE) is proposed for the electromagnetic (EM) scattering or radiation of multiscale metallic targets. To reduce the unknown amount of the conventional SIE for multiscale EM simulation, we apply curved triangular elements and higher order hierarchical vector (HOHV) basis functions to the SIE. Next, to increase the flexibility of geometrical modeling and accelerate the convergence of the presented SIE system for electrically large and multiscale metallic targets, a DDM scheme is further developed to employ a discontinuous Galerkin (DG) approach to glue conformal/nonconformal surface grids between adjacent subdomains. In addition, an interior penalty term is introduced to stabilize the DDM solution, and half edge-based HOHV basis functions are introduced to model the current associated with nonconformal surface elements. Meanwhile, the basis expansion and recombination (BER) technique is introduced to significantly accelerate the matrix-filling and improve the efficiency. The flexibility of basis order selection is further enhanced by the hierarchical characteristic of HOHV bases. Finally, several numerical results are provided to demonstrate the accuracy, efficiency, and flexibility of the proposed HO-DG-DDM.

It is shown that for elliptic boundary value problems of order 2m the condition number of the Schur complement matrix that appears in nonoverlapping domain decomposition methods is of order \(d^{-1}h^{-2m+1}\), where d measures the diameters of the subdomains and h is the mesh size of the triangulation. The result holds for both conforming and nonconforming finite elements.

A non-overlapping domain decomposition method is applied to solve surface integral equations for electromagnetic scattering from cavities. This scheme allows the cavity to be divided into sub-domains and can be solved in a serial or parallel manner. Thus, the memory requirement and CPU time for modeling cavity structures can be dramatically reduced. Moreover, the interior resonance problem is eliminated from this scheme, which occurs in the generalized network formulation.

The Balancing Domain Decomposition by Constraints (BDDC) algorithms, introduced in [4], are nonoverlapping domain decomposition methods. The coarse problems in the BDDC algorithms are given in terms of a set of primal constraints. An important advantage with such a coarse problem is that the Schur complements that arise in the computation will all be invertible. The BDDC algorithms have been extended to many different applications with different discretizations such as [9, 10, 13, 14, 2] and [11, 12].

Three non-overlapping domain decomposition methods are proposed for the numerical approximation of time-harmonic Maxwell equations with damping (i.e., in a conductor). For each method convergence is proved and, for the discrete problem, the rate of convergence of the iterative algorithm is shown to be independent of the number of degrees of freedom.

Nowadays, electromagnetic performance analysis is an integral part of electric and electronic systems development and must be considered during the design phase of the studied systems. Numerous electromagnetic numerical tools exist to solve these systems. However, the complexity of the phenomena to be solved translated by the multitude of scales and numerical methods remains an issue. On the other hand, domain decomposition (DD) methods allow solving a complex problem by breaking it into simpler sub-problems [1]. Generally, the most suitable numerical method is applied to each sub-domain. The global solution is retrieved based on the partial solution of each sub-model through interface conditions. However, most existing methods are in the frequency domain with overlapping interfaces. In the time domain, methods such as temporal hybridization are synchronous and share numerical models [2]. In this work, we rely on [3] to use a temporal domain decomposition method allowing fully asynchronous simulations of the sub-systems while preserving the confidentiality of the numerical models.

We address in detail the numerical simulations of electromagnetic (EM) wave scattering from a mockup partly coated fighter jet in this presentation. The majority part of the fighter jet surface is considered to be perfect electric conductor (PEC). The horizontal stabilizer, vertical stabilizer and the wings are coated with high-density materials, whereas a hollow dielectric radome is located at the front of the aircraft. Due to the nature of unbounded problem domain, and the desire to avoid a three dimensional discretization, we attempt to compute the numerical approximation using the boundary integral equations (BIEs), or the method of moments (MoM). However, it turns out not to be an easy quest. In the presentation, we shall elucidate difficulties that we have encountered and innovative techniques that we have devised during our journey to solve such a challenging mutli-scale EM application.

A spatial domain decomposition method for parabolic optimal control problems

In this paper, we consider the Newton–Schur method in Hilbert space and obtain quadratic convergence. For the symmetric elliptic eigenvalue problem discretized by the standard finite element method and nonoverlapping domain decomposition method, we use the Steklov–Poincaré operator to reduce the eigenvalue problem on the domain into the nonlinear eigenvalue subproblem on , which is the union of subdomain boundaries. We prove that the convergence rate for the Newton–Schur method is , where the constant is independent of the fine mesh size and coarse mesh size , and and are errors after and before one iteration step, respectively. For one specific inner product on , a sharper convergence rate is obtained, and we can prove that . Numerical experiments confirm our theoretical analysis.