0000000000614617
AUTHOR
Juhani Kataja
showing 4 related works from this author
Shape Sensitivity Analysis and Gradient-Based Optimization of Large Structures Using MLFMA
2014
A fast method for computing the action of shape-differentiated electric field integral equation (EFIE) system matrix to a vector is derived exploiting the multilevel fast multipole algorithm (MLFMA). The proposed method is used in conjunction with the adjoint-variable method (AVM) to compute the shape gradient of arbitrary objective functions depending on shape of a metallic scatterer. The method is demonstrated numerically by optimizing the shape of a parabolic reflector illuminated with a half-wave dipole.
Microwave heating of water in a rectangular waveguide: Validating EOF-Library against COMSOL multiphysics and existing numerical studies
2019
The purpose of this work is two-fold: first, we successfully validate our open-source tool EOF-Library, which efficiently couples Elmer FEM and OpenFOAM, against COMSOL Multiphysics, a commercial simulation package; second, we inform about significant discrepancies between our results and the experimental and simulation data found in a series of research papers. We reproduce the previously published numerical simulations wherein microwaves are supplied to a water domain through a rectangular waveguide, inducing convective flow. This is a conjugate problem with weakly coupled electromagnetics, heat transfer and fluid dynamics. It involves effects such as permittivity dependence on temperatur…
An elementary formula for computing shape derivatives of EFIE system matrix
2012
We derive analytical shape derivative formulas of the system matrix representing electric field integral equation discretized with Raviart-Thomas basis functions. The arising integrals are easy to compute with similar methods as the entries of the original system matrix. The results are compared to derivatives computed with automatic differentiation technique and finite differences, and are found to be in excellent agreement.
On shape differentiation of discretized electric field integral equation
2013
Abstract This work presents shape derivatives of the system matrix representing electric field integral equation discretized with Raviart–Thomas basis functions. The arising integrals are easy to compute with similar methods as the entries of the original system matrix. The results are compared to derivatives computed with automatic differentiation technique and finite differences, and are found to be in an excellent agreement. Furthermore, the derived formulas are employed to analyze shape sensitivity of the input impedance of a planar inverted F-antenna, and the results are compared to those obtained using a finite difference approximation.