Sound field modelling using SimulUS

The motivation behind developing the SimulUS beam model was as a tool for the rapid visualisation of ultrasonic fields generated by phased array transducers (both linear and matrix). However, it is possible to model single crystal transducers by defining a 1 by 1 matrix. The present work was carried out using the version released in December of 2005 and was part of a larger validation programme in TWI involving other models. The core of the model is based on Huygen’s discretisation method of evaluating the free field ahead of the sound radiator (Section 2). SimulUS operates principally in the continuous wave(1) mode but a pulse wave expression is incorporated. The model is primarily designed for rapid visualisations of the sound field but it can be used as a pulse wave modelling package. The computing requirements are less intensive when the input waveform is of a single frequency (continuous wave). Hence, in this paper, the evaluation of the performance of SimulUS in its primary continuous wave mode is presented. SimulUS was envisioned for use in applications such as: q Technique development – such that the operator can rapidly evaluate the suitability of a particular setup for the inspection task. q Probe design – confident design of, in particular, phased array probes such that the designer can ensure that the parameters are correctly specified to achieve optimised field properties for the application. q Training – allowing students to understand the basics of phased array ultrasonics and conventional ultrasonics through an interactive learning approach; where the effects of varying the crystal size, pitch, frequency etc on the ultrasonic field generated by the transducer can be understood and even the effects of failed elements modelled. 2. Principles of ultrasonic field models