arXiv:2610.27837v1 Announce Type: new Abstract: The surface acoustic wave (SAW) equations are fundamental in describing the operating principle of SAW devices, which are characterized by high operating frequency, multiphysics coupling, and defined on an unbounded domain. Finite element (FE) simulation is one of the most accurate numerical methods for such devices. However, the method usually leads to ill-conditioned linear systems with a large number of degrees of freedom (DOFs), limiting its application. To address this issue, based on the finite element tearing and interconnecting (FETI) algorithm, this paper proposes a domain decomposition method with iteration numbers stable with respect to number of subdomains, frequency and mesh size, named FETI-SAW. The main novelty is that the Dirichlet preconditioner combined with a Rayleigh-wave-based coarse space is constructed to produce a preconditioned iterative algorithm for the Lagrange multiplier linear system. In some sense, this method reflects the physical essence of the SAW equations. In numerical experiments, we take interdigital transducers (IDT) and SAW resonators as examples to demonstrate the efficiency of the FETI-SAW algorithm. Additionally, the MATLAB and C++ source codes accompanying this paper are provided.