N. Cinosi

A multilevel hierarchical preconditioner for the electric field integral equation

This paper considers the solution of the electric field integral equation (EFIE). Hierarchical conforming bases are developed which are subsequently used in the construction of a multilevel Schwarz type preconditioner. The effectiveness of this approach is demonstrated by the computation of scattering from a range of perfectly conducting objects including spheres, cubes, plates and dihedrals. The resulting schemes are shown to be faster than conventional schemes by approximately an order of magnitude.

CFD Analysis of the Flow in Crud-Coated Nuclear Rod Bundles

This paper presents a methodology to assess the effects of crud surface roughnesses on the normal operation of a PWR reactor.A CFD methodology based on the use of RANS models and the implementation of roughness embedded in STAR-CCM+ CFD code has been developed and applied.A typical PWR reactor case is investigated in details.Results show how the presence of crudded rough rods induces a modification of the flow distribution as compared to the ideal case with clean smooth rods.Notably, these modifications reflect a reduction of the mass flow rate, which in turn has a deteriorating consequence on the efficiency of the fuel-to-coolant heat transfer.© 2014 ASME

A multilevel hierarchical preconditioner technique for multiscale and complex EM scattering bodies

This paper considers the solution of the combined field integral equation (CFIE) for lossy/dielectric problems. Hierarchical conforming bases are developed which are subsequently used in the construction of a multilevel Schwarz type preconditioner. The effectiveness of this approach is demonstrated by the computation of scattering in free space from a range of spheres with different permittivity (non PEC material). The resulting schemes are shown to be faster than conventional schemes.

Application of time-domain BIE to sub-wavelength scattering bodies with finite conductivity

Methods for solving the electromagnetic scattering from bodies with sub-wavelength features are well established. However their application is limited to PEC scattering bodies, whilst when applied to lossy or conducting materials they become inefficient and less desirable. In this paper we extend the capabilities of these fast methods to solve for non-perfect conductors by using the approximation of the Impedance Boundary Condition.

Asymptotic analysis of Surface-Plasmon Whispering-Gallery resonators for large Q-factor

Large Q-factor resonators are essential components in most electronic and photonic systems; that requirement is even more pertinent to the next generation of highly compact nano-photonic integrated circuits. Surface-Plasmon waves combined with Whispering-Gallery modes have the potential to satisfy the dual requirements of small geometry and large Q. A quasi-analytic formulation for SPWG large Q resonator modes is presented in this paper and is demonstrated to be a convenient yet satisfactory procedure to compute device characteristics.

Time-domain bie analysis of large electromagnetic scattering problems with Impedance Boundary Condition

Methods for solving the electromagnetic scattering of computationally large problems in a fast and efficient way are well established. However their application is limited to PEC scattering bodies, whilst when applied to lossy or conducting materials they become inefficient and less desirable. In this paper we extend the capabilities of these fast methods to solve for non-dispersive conductors by using the approximation of the Impedance Boundary Condition.

Integral equation transient analysis of experiments on electromagnetic scattering from sub-wavelength apertures

The scattering of light through arrays of sub-wavelength apertures is studied by using a boundary element method for solving Maxwells equations. Computed results are compared with experiments. There are difficulties in making direct comparisons of measured and computed quantities, but subject to this, reasonable agreement is obtained. Alongside an attempt to reproduce computationally the observed phenomena, one of the objectives of this paper is to investigate the limitations that arise when attempting quantitative computational modeling of the experiment.

Integral Equation Time Domain Analysis of Frequency-dependent Transmission through Aperture Arrays

Whereas a single sub-wavelength aperture transmits little light, much greater transmission is observed through an array of such apertures. Plainly the apertures interact, at a length scale related to their spacing, and encourage the transmission of the light through the small holes. This behaviour is studied via solution of the governing Maxwell equations in the space surrounding the perforated plate, and the field distributions associated with this anomalous transmission are investigated.