Modeling Full Acoustic Field of Guided Waves from Non-Omnidirectional Sources via a 2D-FFT Approach

This work presents a practical and computationally efficient method based on the two-dimensional Fast Fourier Transform (2D-FFT) for modeling the complete acoustic radiation of non-omnidirectional sources in thin plates. In the study of ultrasonic wave propagation, modeling approaches generally follow three paths. Purely theoretical models are often restricted to far-field approximations and simple source distributions. On the other hand, full numerical simulations such as the Finite Element Method (FEM) can model complex geometries with high precision, but they require significant computational time and resources. By implementing a direct spectral domain approach, the direct 2D-FFT method provides a unified solution that describes wave propagation from the source interface to the far-field boundary. To validate this approach, three distinct methods are compared: classical analytical equations, the 2D-FFT method, and FEM simulations. The results demonstrate that while standard analytical theories do not accurately model the acoustic field near the source due to their inherent mathematical simplifications, the 2D-FFT approach closely matches FEM results with high precision in both near and far-field regions. The method allows the direct integration of numerically computed stress distributions into the spectral domain, avoiding the geometric limitations of standard closed-form equations. This flexibility makes it a practical tool for studying complex sensor shapes and optimizing sensor array design.