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A nonstandard Schwarz domain decomposition method is proposed as finite-element mesh truncation for the analysis of infinite arrays. The proposed methodology provides an (asymptotic) numerically exact radiation condition regardless of the distance to the sources of the problem and without disturbing the original sparsity of the finite-element matrices. Furthermore, it works as a multi Floquet mode (propagating and evanescent) absorbing boundary condition. Numerical results illustrating main features of the proposed methodology are shown. This work was supported in part by the National Key Research and Development Program of China under Grant 2016YFE0121600, in part by the China Postdoctoral Science Foundation under Grant 2017M613068, in part by the National Key Research and Development Program of China under Grant 2017YFB0202102, and in part by the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund under Grant U1501501.

We address the task of modelling numerically turbulent flows within random arrays of circular cylinders, relevant for several industrial and environmental applications. Numerical simulations are employed to model infinite domains of randomly placed emergent and rigid cylinders validated by a laboratory database acquired by a PIV system. The main goals are: (i) to discuss the effect of the numerical domain size and the grid resolution on the first and second order moments and (ii) to characterise the spatial distribution of mean flow and turbulence variables in the drag-wake controlled stratum. Five domains of different sizes (9–44 cylinders) and four grid resolutions were independently tested. The results show that the time-averaged velocity field and the Reynolds stress tensor were not significantly affected by the size of the tested numerical domains. The analysis of the grid resolution influence shows how the results improve with mesh refinement, while none of the tested meshes produces un-physical results. The present work provides guidance on the acceptable compromises, in terms of mesh resolution and domain size, when predicting, with eddy resolving computational fluid mechanics tools, first and second-order moments of turbulent flows within infinite arrays or randomly placed cylinders. © 2018 Elsevier Ltd 80 245 261 245-261

A notch antenna, or Vivaldi antennas, or also known as tapered slot antenna (TSA) is widely used as a single radiator but mostly as an array element in transmitting, receiving and combined arrays, focal-plane imaging and other system-oriented broadband applications. Full-wave analysis of such arrays is required that is a big numerical challenge because of large electrical size for such typical problems. Only infinite arrays or very small arrays are treatable with available EM tools. However, all elements of moderate in size arrays can be impacted by edge truncation because of strong mutual coupling within TSA array environment. Thus, accurate performance prediction and design can be achieved through (1) enhancing EM simulation numerical tools and (2) exploring underlying physical phenomenology of array behaviour. We follow both the above ways. This work demonstrates some basic physics related to mutual coupling is small finite arrays.

Array modeling issues are challenging, since they involve large structures (in terms of the wavelength), but also fine details that require much-smaller than wavelength discretizations, and that dominate the frequency response of input parameters.