Analyticity and Stable Computation of Dirichlet–Neumann Operators for Laplace's Equation Under Quasiperiodic Boundary Conditions in Two and Three Dimensions

ABSTRACT Dirichlet–Neumann operators (DNOs) are important to the formulation, analysis, and simulation of many crucial models found in engineering and the sciences. For instance, these operators permit moving‐boundary problems, such as the classical water wave problem (free‐surface ideal fluid flow under the influence of gravity and capillarity), to be restated in terms of interfacial quantities, which not only eliminates the boundary tracking problem, but also reduces the problem's dimension. While these DNOs have been the object of much recent study regarding their numerical simulation and rigorous analysis, they have yet to be examined in the setting of laterally quasiperiodic boundary conditions. The purpose of this contribution is to begin this investigation with a particular focus on the more realistic simulation of two‐ and three‐dimensional free‐surface water waves. Here, we not only carefully define the DNO with respect to these boundary conditions for Laplace's equation, but we also show the rigorous analyticity of these operators with respect to sufficiently smooth boundary perturbations. These theoretical developments suggest a novel algorithm for the stable and high‐order simulation of the DNO, which we implement and extensively test.