Quasi-analytical solution of two-dimensional Helmholtz equation

Abstract

• Formulation of transformed Helmholtz equation. • Illustration of conformal mapping to solve the Helmholtz equation. • Illustration of quasi-analytical solution of Helmholtz equation for non-trivial shapes. The two-dimensional Helmholtz differential equation governs vibrational problems for a thin membrane and is therefore well studied. Analytical solutions are limited to particular domain shapes, so that in general numerical methods are used when an arbitrary domain is considered. In this paper, a quasi-analytical solution is proposed, suitable to be applied to an arbitrary domain shape. Concretely, the Helmholtz equation is transformed to account for a conformal map between the shape of the physical domain and the unit disk as canonical domain. This way, the transformed Helmholtz equation is solved exploiting well known analytical solutions for a circular domain and the solution in the physical domain is obtained by applying the conformal map. The quasi-analytical approach is compared to analytical solutions for the case of a circular, elliptic and squared domain.