SIAM Undergraduate Research Online

Volume 18

In This Volume

  • A Laplace Equation on a Rectangle With Mixed Boundary Conditions

    Published electronically February 5, 2025

    DOI: 10.1137/24S1691600

    Authors

    Elias Hohl (Corresponding author – ETH Zürich)

    Project Advisors

    Giovanni Felder (ETH Zürich)

    Abstract

    We find analytical solutions of the Laplace equation on a rectangular domain with Dirichlet-Neumann boundary condition type transition occurring on a side of the rectangle. The problem can be tackled either by cutting the domain in two parts and solving the obtained coupled Laplace equations using a Fourier series approach, or by creating a conformal mapping based on Christoffel-Schwarz and Mobius transformations between the original domain and another rectangular domain where the solution of the problem is less challenging. Apart from solving for the temperature field, we also compute a coefficient, dependent only on the geometry of the domain, from which the thermal resistance of a system with the given cross-section can be computed. We conduct an experiment to confirm the validity of our model. Using our results from the Christoffel-Schwarz method, we derive regularity results for the Fourier coefficients of the coupling method. We not only determine the order of decay, but also find formulas for explicit upper bounds of the absolute value of the coefficients. These results can be used to obtain maximum error bounds for a numerical computation considering only a finite number of Fourier coefficients. Furthermore, we prove that the solutions obtained via the coupling method converge to the actual solution.

  • Modeling Traffic Conditions to Determine Shortest Path

    Published electronically January 10, 2025

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