Weakly Nonlinear Propagation in Thermoacoustic Engines: A Numerical Study of Higher Harmonics Generation up to the Appearance of Shock Waves

Though thermoacoustic engines usually operate at high acoustic amplitude, they rarely exhibit strong deformation of the wavefront due to nonlinear propagation. It has however been demonstrated experimentally that obtaining shock waves in thermoacoustic engines is possible under specific conditions. This paper aims at presenting a simple description of the periodic steady-state operation of thermoacoustic engines describing the wave steepening process leading to shock wave formation. Results of numerical simulations are compared to experimental data in different engine configurations, and model improvements are proposed to reach a realistic description of the weakly nonlinear propagation in thermoacoustic engines.