OpenPSTD: The open source implementation of the pseudospectral time-domain method

An open source implementation of the pseudospectral time-domain method for the propagation of sound is presented, which is geared towards applications in the built environment. Being a wavebased method, PSTD captures phenomena like diffraction, but maintains efficiency in processing time and memory usage as it allows to spatially sample close to the Nyquist criterion, thus keeping both the required spatial and temporal resolution coarse. As a first step, in this implementation it has been opted to model the boundary geometry as a composition of rectangular two-dimensional subdomains, hence initially restricting the implementation to orthogonal and two-dimensional situations. The strategy of using subdomains divides the problem domain into local subsets, which enables the simulation software to be built according to Object-Oriented Programming best practices and allows room for further computational parallelization. The software is built using the open source components, Blender, Numpy and Python, and has been published under an open source license itself as well. Research is still being done on strategies to model non-orthogonal geometries and curvilinear grid generation to allow arbitrary geometries as input. Furthermore, impedance boundary conditions and source directivity will be added in subsequent installments, based on current ongoing research, as well as local grid refinement, a moving medium and further performance improvements by implementing GPU computing. Especially when the implementation is extended into a three-dimensional solution, these performance improvements are expected to be essential in order to be fast enough to ensure usability in practice.