Efficient acoustic modelling of large acoustic spaces using finite difference methods.

Time domain methods for solving wave based acoustic models have been of continued interest and development since early work by key figures such as Bottledooren, as these methods can provide a simple and flexible approach for simulating a wide range of acoustic phenomena such as room modes. The nature of many time domain difference methods present significant computational resource requirements, as the size, sampling rate and inherent stability of the simulation has a distinct impact on the memory and execution time required for the simulation to give a satisfactory result. In this study the execution speed is analysed, for variations of the finite difference time domain method that may provide some increase in computation speed for large domains. It is suggested that leveraging a dynamic windowing method may reduce total computation time for some simulations, by decreasing the number of computations per time-step in the early stage of a simulation.N/

Comparative study of models of impedance boundary conditions in acoustic problems

En este artículo se presentan distintas soluciones para la implementación numérica de condiciones de contorno de impedancia (reactancia local) en problemas acústicos. Para ello se analizan 2 tipos de ecuaciones: las ecuaciones de Euler y la ecuación de ondas, y se estudian diferentes soluciones para los contornos tanto en algoritmos de diferencias finitas en el dominio del tiempo (FDTD) como en algoritmos pseudo-espectrales en el dominio del tiempo (PSTD). El análisis de las distintas propuestas numéricas existentes en la literatura se realiza mediante exhaustivos experimentos numéricos que permiten estudiar el comportamiento absorbente de las distintas condiciones de contorno en función de la frecuencia y del ángulo de las ondas incidentes. Este novedoso estudio comparativo permite al ingenierio acústico escoger el modelo numérico que más se adapte a sus necesidades.In this paper, different implementations of numerical locally reacting boundary conditions are studied for acoustic problems. In this comparative study we analyze two types of equations, the Euler equations and the wave equation. We also analyze both finite-differences time-domain (FDTD) algorithms, and pseudo-spectral time domain (PSTD) numerical schemes. We compare different numerical implementations existing in the literature by means of exhaustive numerical experiments. These numerical experiments allow for the study of the absorbing properties of the different schemes as a function of the frequency and the angle of the incident sound waves. This novel comparative study will help the acoustic engineer in order to choose the proper numerical scheme for his/her simulations.Peer Reviewe

Energy saving by reducing motor rating of Sucker-Rod Pump systems Energy

Acknowledgments The research in this paper is supported and funded by programs with China Scholarship Council (Grant 201708130108), and National Natural Science Foundation of China (Grant 51974276).Peer reviewedPostprin