A multipole method for Schwarz-Christoffel mapping of polygons with thousands of sides

A method is presented for the computation of Schwarz-Christoffel maps to polygons with tens of thousands of vertices. Previously published algorithms have CPU time estimates of the order O(N^3) for the computation of a conformal map of a polygon with N vertices. This has been reduced to O(N log N) by the use of the Fast Multipole Method and Davis's method for solving the parameter problem. The method is illustrated by a number of examples, the largest of which has N approx 2 × 10^5

Boundary Conditions by Schwarz-Christoffel Mapping in Anatomically Accurate Hemodynamics

Appropriate velocity boundary conditions are a prerequisite in computational hemodynamics. A method for mapping analytical or experimental velocity profiles on anatomically realistic boundary cross-sections is presented. Interpolation is required because the computational and experimental domains are seldom aligned. In the absence of velocity information one alternative is the adaptation of analytical profiles based on volumetric flux constraints. The presented algorithms are based on the Schwarz-Christoffel (S-C) mapping of singly or doubly connected polygons to the unit circle or an annulus with unary external radius. S-C transformations are combined to construct a one-to-one invertible map between the target surface and the measurement domain or the support of the source analytical profile. The proposed technique permits us to segment each space separately and map one onto the other in its entirety. Tests are performed with normal velocity boundary conditions for computational simulations of blood flow in the ascending aorta and cerebrospinal fluid flow in the spinal cavity. Mappings of axisymmetric velocity profiles of the Womersley type through a simply connected circular pipe as well as through a doubly connected circular annulus, and interpolations from in-vivo phase-contrast magnetic resonance imaging velocity measurements under instantaneous volumetric flux constraints are considere

Nelikulmion modulin numeerinen laskenta

The module of a quadrilateral is a positive real number which divides quadrilaterals into conformal equivalence classes. This is an introductory text to the module of a quadrilateral with some historical background and some numerical aspects. This work discusses the following topics: 1. Preliminaries 2. The module of a quadrilateral 3. The Schwarz-Christoffel Mapping 4. Symmetry properties of the module 5. Computational results 6. Other numerical methods Appendices include: Numerical evaluation of the elliptic integrals of the first kind. Matlab programs and scripts and possible topics for future research. Numerical results section covers additive quadrilaterals and the module of a quadrilateral under the movement of one of its vertex.Nelikulmion moduli on positiivinen reaaliluku, joka jakaa nelikulmiot konformisiin ekvivalenssi luokkiin. Tämä on johdanto teksti nelikulmion moduliin ja sen numeeriseen laskentaan. Lisäksi työssä on näiden alojen historiaa. Työssä käsitellään mm. seuraavia asioita: 1. Esitiedot 2. Nelikulmion modulin määritelmä 3. Schwarz-Christoffel kuvaus 4. Nelikulmion modulin symmetriaominaisuuksia 5. Laskennallisia tuloksia 6. Muita numeerisia menetelmiä Liitteet sisältävät: Elliptisten, ensimmäisen luokan, integraalien numeerinen laskeminen. Matlab ohjelmia, joita on käytetty työssä ja ehdotuksia tutkimuskohteiksi. Laskennallisissa tuloksissa osiossa tutkitaan summautuvia nelikulmioita ja nelikulmion modulia. Lisäksi tutkitaan miten nelikulmion moduli muuttuu kun yksi sen kärkipiste liikkuu

Study of the Laplacian eigenvalues of fractal sets

This thesis presents an example of known discretization methods for spectral problems in partial dierential equations and it is applied with some computations in planar domains with irregular (non-smooth) and self-similar boundary