Investigation on Rijke pipe's acoustic characteristics by numerical simulation:modeling the pulsing flow field coupled the inner of pipe with its outer space

Based on the results of fluid dynamics,heat transfer and acoustics,a Computational Fluid Dynamics(CFD) method was utilized to study the acoustic characteristics and self-excited pulsation mechanism inside a Rijke pipe.To avoid settling the irrational boundary conditions of the finite-amplitude standing wave in Rijke thermoacoustic system, the simulation modeling in the flow field,which coupled the inner of pipe with its outer space was carried out to replace the traditional way in form of internal flow field numerical investigations.A hypothesis for heat source in energy equation including the relationship on unsteady heat of air around heat source,oscillation pressure and oscillation velocity was presented.To reflect the essence of Rijke pipe,simulation on self-excited oscillation was obtained by means of its own pulsation of pressure,velocity and temperature.This method can make the convergence process steady and effectively avoid the divergence.The physical phenomenon of self-excited Rijke pipe was analyzed.Moreover,the mechanisms on Rijke pipe's self-excited oscillation were explained.Based on this method,comparative researches on the acoustic characteristic of Rijke pipe with different size and different shape of nozzle were performed.The simulation results agreed with the experimental data satisfactorily.Resultsshowed that this numerical simulation can be used for studying the sound pressure of nozzle for the engineering application of Rijke pipe.