Numerical Simulation of Unsteady Interactions between Flow, Heat Conduction and Acoustics within a Rijke Tube

The oscillations within a Rijtke tube are calculated from first principles in the simulations presented in this paper: the unsteady conservation equations of mass, momentum and energy, together with appropriate boundary conditions, are solved simultaneously by means of a finite difference method. No further assumptions, as they are made in numerous other approaches, are necessary, e.g., regarding the periodic non-linear heat transfer to the air, or the time lag between heat flux and pressure oscillation. Accordingly, this is a complete simulation model that provides these quantities as results. A comparison between calculated and experimental results shows good agreement between the various data. The oscillations within Rijke tubes are excited by a mechanism comparable to numerous kinds of self-excited combustion oscillations in burners even though the conditions prevailing there are invariably much more complex. Since oscillations in combustion chambers cause numerous problems for certain industries, the method used in this paper is now being employed for ongoing work on simulating this type of oscilllation, the long-term goal being to create a tool allowing the potential appearance of self-excited oscillations to be assessed while system development is still in progress.