Comparison of different methods to couple nonlinear source descriptions in the time domain to linear system descriptions in the frequency domain—Application to a simple valveless one-cylinder cold engine

In duct acoustics the fundamental sound generating mechanisms must often be described by nonlinear time domain models. A linear frequency domain model is in many cases sufficient for describing the sound propagation in the connected duct system. This applies both for fluid machines such as IC-engines and compressors and for musical wind instruments. Methods for coupling a nonlinear source description to a linear system description have been proposed by several authors. In this paper some of those methods are compared concerning accuracy, calculation time and the possibility to perform parametric studies. The model problem used is a simple piston–restriction system connected to a linear system with varying complexity. The piston and restriction are considered as the source part and are modelled nonlinearly.