流体谐振型时均流诱导声振荡二维数值模拟

2D CFD simulation of fluid-resonant acoustic oscillation induced by mean flow

针对时均流通过十字型深腔结构时产生的"流体谐振型"声振荡现象,采用大涡模拟方法进行数值模拟研究.发现动态Smagorinsky-Lilly模型和壁面自适应局部涡黏模型均能较好描述振荡频率和压力振幅随时均流速的变化规律,但后者对雷诺应力预测不足.计算结果表明,在支管内会形成典型的驻波声场,并随着流速的变化表现出不同的水力模态和声学模态特征.在此基础上,揭示流体谐振型时均流诱导声振荡的发生机理:驻波声场影响涡结构的脱落以及运动轨迹,而涡结构在运动过程中向谐振腔内的声场输出能量,完成两者的耦合作用.

To study the fluid-resonant acoustic oscillation phenomenon induced by the mean flow in a crossjunction deep cavity, the Large-Eddy Simulation （I.ES） is applied. The result indicates that the dynamic Smagorinsky-Lilly model and the wall-adapted local eddy-viscosity model both can predict the changing rule of oscillation frequency and pressure amplitude. But the latter gives smaller Reynolds stress. It is shown that a standing wave acoustic field forms in the branch tube, and the hydrodynamic mode and acoustic mode change with the mean flow velocity. On this basis, the mechanism of the fluid-resonant oscillation induced by the mean flow is revealed, showing that vortex shedding at the upstream edge of cavity and vortex movement locus are significantly influenced by the acoustic field. On the other hand, vortex structures transfer energy into the acoustic field as they move along the opening of the cavity, thus accomplishing the coupling between the mean flow and the acoustic field.