Numerical investigation of velocity and temperature distributions in thermoacoustic stacks

Energy conversion based on the interaction of acoustic fluctuations in thermal and viscous boundary layers offers a promising possibility for reducing fossil energy resources. Machines based on this so-called thermoacoustic effect can be used as heat engines as well as heat pumps or refrigerators. However, the problem with the implementation of such systems is the insufficient understanding of the various phenomena (e. g. turbulence) of thermally excited flows. Numerical methods, such as CFD, are established for the optimization and further development of thermoacoustic systems due to increasing computational capacities. The foundation for optimizations is a reliable and realistic prediction of the flow and heat transfer process in thermoacoustic systems. Therefore, in this study, different approaches based on the RANS equations are investigated with the use of the CFD code ANSYS Fluent®. In addition to two standard eddy-viscosity models, two model extensions are implemented in the CFD code. Extensive measurement data based on time-resolved laser-assisted flow measurements are used for the validation of the investigated turbulence models. As the studies show, the standard eddy-viscosity models provide a good prediction of the velocity and temperature profiles. However, it can be pointed out that both the elliptic relaxation model (V2F) and the local formulation of the Transition SST model bring an improvement, especially in the interpretation of non-linear effects.