指数型谐振管内非线性声场的模拟研究

Numerical simulations of the nonlinear acoustical field in an exponential shaped thermoacoustic resonator

采用气体动理学方法模拟研究五种不同驱动强度下,=0的圆直热声谐振管和=2 2的指数型热声谐振管内的非线性声场特征。研究发现:指数型管能抑制激波及声饱和现象,但管内会出现尖峰现象。尖峰处的压力波形发生了畸变;它们是非线性的能量传递与各种耗散的竞争过程中产生的不同形态的波特征;当活塞驱动位移幅值400μm时,指数型管内压力振幅增长速度明显下降。

The gas kinetic scheme is used to simulate the nonlinear acoustic filed in two kinds of exponential shaped resonators of m= 0 （i.e. cylindrical resonator） and m =2.2, respectively. By comparing the characters of acoustic fields in the two different resonators driven by a vibrating piston with five different driving ampli- tudes, some nonlinear phenomena in exponential shaped resonator with m = 2.2 are revealed. The research shows a fact that the exponential tube can inhibit the phenomena of shock wave. However, some nonlinear phenomena such as the spike phenomenon will occur with the increasing driving intensity in the exponential shaped resonator with m = 2.2, and the waveforms of pressure at spikes are all distorted. The spike phe- nomenon and waveform distortion are different acoustic wave forms which are induced by the competition of nonlinear energy transfer with all sorts of dissipative phenomena. When the driving amplitude of piston greater than or equal to 400um, the waveforms of pressure in exponential shaped resonator with m = 2.2 at steady state are so distorted that the pressure amplitude growth slowed significantly.