Computational thermoacoustic simulation of minor losses through a sudden contraction and expansion

This paper describes a simulation of unsteady compressible flow in a resonator driven by a high amplitude standing wave. This work is a preliminary study of the physical processes leading to minor losses in ther-moacoustic devices. A brief description of thermoa-coustic prime movers and refrigerators is given first. This provides a simple explanation of thermoacous-tic heat-pumping. A two-dimensional simulation of a simple resonator with a large change in cross-sectional area is described. The geometry and the computational domain match those of a complementary experiment. Some details of the numerical algorithms and the parallel implementation are included. Results are presented for the average and unsteady flow in the resonator. It is shown that the oscillating flow near the sudden expansion/contraction induces a synthetic jet flow in the resonator. The mean pressure difference across the expansion is determined and the relative contributions of the excess second-order pressure and the total pressure losses due to the generation of vor-ticity are estimated.