Ales Janka

Ales Janka
University of Applied Sciences and Arts Western Switzerland · Faculty of Engineering and Architecture

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28
Publications
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480
Citations

Publications

Publications (28)
Article
We report the development and application of a refined version of the classical Cassie- Baxter wetting model for the prediction of surface topographies with superomniphobic traits. The sagging height defined through the capillary length was utilized to assess the relation between a curved liquid-air interface and the surface texture. The wettabilit...
Article
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Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insigh...
Article
We present here a model for simulating the ferromagnetic screening effect in thin steel plates. We exhibit a domain decomposition method to solve this problem by using only Laplace equations. We then apply this on an academic situation of a steel plate placed in front of a linear conductor and on an industrial application in aluminum production. Mo...
Article
Morphogenesis occurs in 3D space over time and is guided by coordinated gene expression programs. Here we use postembryonic development in Arabidopsis plants to investigate the genetic control of growth. We demonstrate that gene expression driving the production of the growth-stimulating hormone gibberellic acid and downstream growth factors is fir...
Article
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In this paper, we present a mathematical modeling of some magnetohydrodynamic effects arising in an aluminum production cell as well as its numerical approximation by a finite element method. We put the emphasis on the magnetic effects which live in the whole three dimensional space and which are solved numerically with a domain decomposition metho...
Chapter
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We present two numerical methods for the simulation of ferromagnetic phenomenons in a metallic plate, with or without holes. First we briefly recall the physical model we use for describing the ferromagnetic phenomenon. This model is based on the use of a scalar potential while other models rather use a vector potential as in [1] or [2]. Next we pr...
Article
We give a convergence estimate for a Petrov-Galerkin Algebraic Multigrid method. In this method, the prolongations are defined using the concept of smoothed aggregation while the restrictions are simple aggregation operators. The analysis is carried out by showing that these methods can be interpreted as variational Ritz-Galerkin ones using modifie...
Article
Full-text available
We discuss advantages of using algebraic multigrid based on smoothed aggregation for solving indefinite linear problems. The ingredients of smoothed aggregation are used to construct a black-box monolithic multigrid method with indefinite coarse problems. Several techniques enforcing inf–sup stability conditions on coarse levels are presented. Nume...
Article
We discuss the advantages of using algebraic multigrid based on smoothed aggregation for solving indefinite linear problems. The ingredients of smoothed aggregation are used to construct a black-box monolithic multigrid method with indefinite coarse problems. Although we discuss some techniques for enforcing the uniform inf-sup stability on all coa...
Article
encountered in the elec- trolysis of aluminium. During the process of aluminium production, high densities of electric current are used to produce pure liquid aluminium out of aluminium oxide. These currents induce huge magnetic fields, which interact with the liquid aluminium, causing important flows inside the electrolytic cell. The forced flow m...
Article
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This article is a sequel of [J.-A. Désidéri, Hierarchical optimum-shape algorithms using embedded Bézier parameterizations, in: Y. Kuznetsov et al., (Ed.), Numerical Methods for Scientific Computing, Variational Problems and Applications, CIMNE, Barcelona, 2003], in which we defined formally a hierarchical shape optimization method based on a multi...
Article
This presentation aims at reporting numerical experiments of multipoint aero-dynamic optimization of a business jet wing conducted by Piaggio Aero Industries in col-laboration with INRIA. The method incorporates constraints of particular interest to the pre-industrial case and illustrates the gain realized in aerodynamic performance.
Article
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A finite-volume based linear multigrid algorithm is proposed and used within an implicit linearized scheme to solve Navier–Stokes equations for compressible laminar flows. Coarse level problems are constructed algebraically based on convective and diffusive fluxes, without the knowledge of coarse geometry. Numerical results for complex 2D geometrie...
Article
Full-text available
On réalise l'optimisation de forme d'une voilure d'avion supersonique dans le but de réduire un critère lié au bang sonique tout en préservant la performance aérodynamique. On teste numériquement un algorithme de gradient et un algorithme génétique (AG) dont les mérites sont complémentaires, et on construit un algorithme hybride. Le cas test se rév...
Article
This article is made of two parts. In the first, we solve an optimum shape design problem in aerodynamics. In the supersonic regime, we minimize a functional blending lift and drag constraints with a bang criterion and a geometrical penalty. The algorithm is a standard hybridization strategy consisting of operating a gradient-based op- timizer afte...
Article
Full-text available
A versatile parameterization technique is developed for 3D shape optimization in aerodynamics. Special attention is paid to construct a hierarchical parameterization by progressive enrichment of the parametric space. After a brief review of possible approaches, the free-form deformation framework is elected for a 3D tensorial Bézier parameterizatio...
Article
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In this report, the Cascadic Multigrid method (CMG), viewed as a «one-way» multigrid method not involving pre-smoothing or restriction steps, is defined and tested in the case of a simple 2D advection-diffusion problem. Jacobi and Gauss-Seidel smoothers are employed. While the Cascadic Multigrid method is very effective for relatively small Reynold...
Article
We give a discrete H error estimate of a finite volume discretization of the H regular Poisson problem on nonstructured meshes. The discrete finite volume solution is compared to a L weighted projection of the exact solution to the finite volume space. As the projection is stable in L (unlike in standard finite volume estimates which use Taylor's e...
Article
We generalize the overlapping Schwarz domain decomposition method to problems of linear elasticity. The convergence rate independent of the mesh size, coarse-space size, Korn's constant and essential boundary conditions is proved here. Abstract convergence bounds developed here can be used for an analysis of the method applied to singular perturbat...
Article
Full-text available
We give a convergence estimate for a Petrov-Galerkin Algebraic Multigrid method. In this method, the prolongations are defined using the concept of smoothed aggregation while the restrictions are simple aggregation operators. The analysis is carried out by showing that these methods can be interpreted as variational Ritz-Galerkin ones using modifie...
Article
. We give a convergence estimate for a Petrov-Galerkin Algebraic Multigrid method. In this method, the prolongations are defined using the concept of smoothed aggregation while the restrictions are simple aggregation operators. The analysis is carried out by showing that these methods can be interpreted as variational Ritz-Galerkin ones using modif...
Article
We present the construction and report on the experimentation of a shape- optimization method applied to the aerodynamic design of a transonic or supersonic busi- ness jet. The main numerical ingredients are: a 3D unstructured-grid compressible-flow finite-volume solver, free-form deformation approach for shape and mesh movement based on self-adapt...
Article
A Full and Adaptive Multi-Level Optimum-Shape Algrithm (FAMOSA) is proposed for the minimization of a functional constrained by a PDE state equation in a domain with shape-dependent boundaries [2]. The state equation is discretized over...
Article
otropic or anisotropic coarsening. For anisotropic(directional) coarsening, the prefered (local) direction can be given eg. by a normal vectorto the surface of a layer.4. Fix each node in an odd layer (layer=1,3,. . . ) and remesh the finest mesh (while preservingthe fixed nodes) by an existing mesh-generator MTC. This mesher proceeds in a local wa...
Article
We generalize the results of Kwak [16] and Bramble, Ewing, Pasciak and Shen [2]and discuss convergence proofs for several multigrid algorithms in a framework of nested multigridspaces and noninherited quadratic forms for structured finite-volume schemes for SPD problems.Convergence proofs are stated for W-cycle with only piecewise constant transfer...

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