Sound wave propagation in rarefied molecular gases
Sound wave propagation in rarefied molecular gases
复制标题
DOI：
10.1017/jfm.2023.698
复制
发表时间：
2023-10-20
影响因子：
3.7
通讯作者：
Zhang，Yonghao
中科院分区：
文献类型：
--
作者：
Li，Shaokang;Su，Wei;Zhang，Yonghao
数值研究了声波在微通道内稀薄分子气体流动中的传播。我们首先验证了所采用的动力学模型对实验结果，然后系统地研究了气体阻尼和表面力的换能器，以及在有限空间中的共振/反共振。为了量化的平移和内部能量的有限弛豫率对波传播的影响，我们研究了体积粘度和热导率的作用，在很宽的范围内的稀疏和振荡频率的深度。结果表明，体粘滞系数只对高振荡下滑移区的压力幅值及其共振频率有影响。此外，当分子气体的体积粘度大时，内部自由度被冻结，导致声波在分子气体中的压力振幅与在单原子气体中相同。同时，在所有的模拟流动中，导热系数对压力幅值的影响都是有限的。在热声波的情况下，我们证明了Onsager-Casimir倒易关系对分子气体也成立，即温度变化引起的压力偏差等于板振荡引起的热通量。我们的研究结果使声波在分子气体中的传播，这可能有助于纳米/微米尺度的设备的设计增强的理解。
Sound wave propagation in rarefied flows of molecular gases confined in micro-channels is investigated numerically. We first validate the employed kinetic model against the experimental results and then systematically study the gas damping and surface force on the transducer as well as the resonance/anti-resonance in confined space. To quantify the impact of the finite relaxation rates of the translational and internal energies on wave propagation, we examine the roles of bulk viscosity and thermal conductivity in depth over a wide range of rarefactions and oscillation frequencies. It is found that the bulk viscosity only exerts influence on the pressure amplitude and its resonance frequency in the slip regime in high oscillations. In addition, the internal degree of freedom is frozen when the bulk viscosity of a molecular gas is large, resulting in the pressure amplitude of sound waves in the molecular gas being the same as in a monatomic gas. Meanwhile, the thermal conductivity has a limited influence on the pressure amplitude in all the simulated flows. In the case of the thermoacoustic wave, we prove that the Onsager–Casimir reciprocal relation also holds for molecular gases, i.e. the pressure deviation induced by the temperature variation is equal to the heat flux induced by the plate oscillation. Our findings enable an enhanced understanding of sound wave propagation in molecular gases, which may facilitate the design of nano-/micro-scale devices.