Interaction of a Shock wave with a Homogeneous Field of Acoustic Waves: Theory and Simulation

当波在流体中的运动速度超过声速时，就会产生冲击波。 冲击波与可压缩湍流的相互作用与广泛的工程应用有关，包括航空（超音速飞行和推进）、能源（聚变）、医学（冲击波碎石术）和空间物理学（星星形成和超新星爆炸）。 了解冲击波与均匀声场之间的相互作用（冲击/声学相互作用）具有重要的理论和实际意义。 考虑到激波与背景噪声共存是在超音速风洞中进行的任何实验中几乎不可避免的特征，激波/噪声干扰的研究对于超音速风洞中背景噪声扰动的表征以及将在有噪声的超音速风洞中获得的测量数据外推到自由飞行特别重要。通过参与密苏里州ST学生多样性、外展和妇女？的计划，以吸引学生考虑在干领域的职业生涯。在这个研究项目中，显着的流动特性与一个均匀的领域的声波通过一个名义上正常的冲击波量化使用直接的数值模拟和线性相互作用分析。成熟的非线性模拟和线性分析是由边界层声辐射的前体数值数据库，提供入射声场具有高度的物理现实性和适用性。这项研究推进了激波/声学相互作用的最新知识，包括（1）激波后波动的一般统计和频谱特征及其对流动参数的依赖性;（2）线性和非线性机制之间的区别;（3）与总压相关的传递函数以及各个Kovasznay模式对激波后总压的贡献。这项研究有助于从根本上理解的冲击波与湍流场的相互作用，通过表征其行为在纯湍流极限和补充现有的研究与涡主导的入射湍流场的冲击/湍流相互作用。该项目还为在嘈杂的超音速风洞中用侵入式探头测量风洞自由振动噪声和阐明设施噪声对在这种风洞中获得的实验数据的影响提供了基础。

A shock wave occurs when a wave moves faster than the speed of sound in a fluid. The interaction of a shock wave with compressible turbulence is relevant to a wide range of engineering applications including aeronautics (supersonic flight and propulsion), energy (fusion), medicine (shock wave lithotripsy), and space physics (star formation and supernovae explosions). Understanding the physics of the interaction between a shock wave and a homogeneous field of acoustic waves (shock/acoustics interaction) are of major theoretical and practical importance. Given that the coexistence of shock waves with background acoustic noise is an almost unavoidable feature for any experiments conducted in supersonic wind tunnels, the study of shock/acoustics interaction is particularly important to the characterization of background acoustic disturbances in supersonic wind tunnels and to the extrapolation of measurement data obtained in noisy supersonic wind tunnels to free flight. The experiences and results gained from the research effort are being incorporated into education activities including classroom teaching, research training, and outreach activities via involvement in Missouri S&T Student Diversity, Outreach and Women?s Programs in order to engage students to consider careers in STEM fields. In this research project, significant flow characteristics associated with a homogeneous field of acoustic waves passing through a nominally normal shock wave are quantified using direct numerical simulations and linear interaction analysis. The full-fledged nonlinear simulations and the linear analysis are enabled by a pre-cursor numerical database of boundary-layer acoustic radiation that provides incident acoustic fields with a high degree of physical realism and applicability. This study advances the state of the art knowledge of shock/acoustics interaction, including (1) the generic statistical and spectral features of the post-shock fluctuations and their dependence on flow parameters; (2) the distinctions between linear and nonlinear mechanisms; and (3) the transfer function associated with the total pressure and the contribution of individual Kovasznay modes to the post-shock total pressure. This research contributes to the fundamental understanding of the interaction of a shock wave with a field of turbulence by characterizing its behaviors in the pure dilatational limit and complements existing studies of shock/turbulence interaction with a vorticity-dominated incident turbulent field. The project also provides the basis for measuring tunnel freestream noise with intrusive probes in noisy supersonic wind tunnels and for elucidating the impact of facility noise on the experimental data obtained in such wind tunnels.