Abstract
This paper presents a deep reflection on the advective wave equations for velocity vector and dilatation discovered in the past decade. We show that these equations can form the theoretical basis of modern gas dynamics, because they dominate not only various complex viscous and heat-conducting gas flows but also their associated longitudinal waves, including aero-generated sound. Current aeroacoustics theory has been developing in a manner quite independently of gas dynamics; it is based on the advective wave equations for thermodynamic variables, say the exact Phillips equation of relative disturbance pressure as a representative one. However, these equations do not cover the fluid flow that generates and propagates sound waves. In using them, one has to assume simplified base-flow models, which we argue is the main theoretical obstacle to identifying sound source and achieving effective noise control. Instead, we show that the Phillips equation and alike is nothing but the first integral of the dilatation equation that also governs the longitudinal part of the flow field. Therefore, we conclude that modern aeroacoustics should merge back into the general unsteady gas dynamics as a special branch of it, with dilatation of multiple sources being a new additional and sharper sound variable.
摘要
本文是对过去十年发现的速度矢量和胀量的运流波动方程的反思和深化. 结果表明, 矢量速度方程和胀量方程不仅能刻画黏 性传热流体的各种复杂流动本身, 而且能刻画包括气动噪声在内的各种纵波在复杂流场中的非线性形成与演化, 因此它们可以构成现 代气体动力学的理论基础. 现代气动声学理论的建立是基于热力学变量的运流波动方程(例如Phillips方程), 其发展完全独立于气体动 力学. 然而, 基于热力学变量的方程不能预测产生并传播声波的各种复杂流动本身, 使得人们不得不代之以过度简化的模型, 因而导致 了声源识别的不确定性和噪声难以控制. 我们证明, Phillips方程和同类基于热力学变量的方程只不过是胀量方程的一次积分, 后者主 管了流动的纵场部分. 因此, 现代气动声学作为气体动力学的一个分支应该重新融合到气体动力学的统一理论框架之中, 同时具有多 种物理源的胀量也应该视为新的且更普适的声学变量.
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References
F. Mao, Y. P. Shi, L. J. Xuan, W. D. Su, and J. Z. Wu, On the governing equations for the compressing process and its coupling with other processes, Sci. China-Phys. Mech. Astron. 54, 1154 (2011).
F. Mao, L. L. Kang, J. Z. Wu, J. L. Yu, A. K. Gao, W. D. Su, and X. Y. Lu, A study of longitudinal processes and interactions in compressible viscous flows, J. Fluid Mech. 893, A23 (2020).
R. D. Zucker, and O. Biblarz, Fundamentals of Gas Dynamics, 3rd ed. (John Wiley & Sons, New Jersey, 2020).
R. G. Davies, Aerodynamics Principles for Air Transport Pilots (CRC Press, Boca Raton, 2020).
H. Schlichting, and K. Gersten, Boundary Layer Theory, 9th ed. (Springer, Berlin, 2017).
M. J. Lighthill, On sound generated aerodynamically I. General theory, Proc. R. Soc. Lond. A 211, 564 (1952).
M. J. Lighthill, On sound generated aerodynamically II. Turbulence as a source of sound, Proc. R. Soc. Lond. A 222, 1 (1954).
N. Peake, and A. B. Parry, Modern challenges facing turbomachinery aeroacoustics, Annu. Rev. Fluid Mech. 44, 227 (2012).
M. Ihme, Combustion and engine-core noise, Annu. Rev. Fluid Mech. 49, 277 (2017).
S. Karabasov, L. Ayton, X. Wu, and M. Afsar, Advances in aeroacoustics research: Recent developments and perspectives, Phil. Trans. R. Soc. A. 377, 20190390 (2019).
J. W. Jaworski, and N. Peake, Aeroacoustics of silent owl flight, Annu. Rev. Fluid Mech. 52, 395 (2020).
H. Daryan, F. Hussain, and J. P. Hickey, Sound generation mechanism of compressible vortex reconnection, J. Fluid Mech. 933, A34 (2022).
J. Wu, L. Liu, and T. Liu, Fundamental theories of aerodynamic force in viscous and compressible complex flows, Prog. Aerosp. Sci. 99, 27 (2018).
J. J. Alonso, and M. R. Colonno, Multidisciplinary optimization with applications to sonic-boom minimization, Annu. Rev. Fluid Mech. 44, 505 (2012).
D. Y. Ma, Modern Acoustic Theory Foundation (Science Press, Beijing, 2004).
G. K. Vallis, Essentials of Atmospheric and Oceanic Dynamics, illustrated ed. (Cambridge University Press, Cambridge, 2019).
J. E. Ffowcs Williams, Aeroacoustics, Annu. Rev. Fluid Mech. 9, 447 (1977).
P. Jordan, and Y. Gervais, Subsonic jet aeroacoustics: Associating experiment, modelling and simulation, Exp. Fluids 44, 1 (2008).
F. Mao, Y. P. Shi, and J. Z. Wu, On a general theory for compressing process and aeroacoustics: Linear analysis, Acta Mech. Sin. 26, 355 (2010).
H. Babinsky, and J. K. Harvey, Shock Wave-Boundary-Layer Interactions (Cambridge University Press, Cambridge, 2011).
O. M. Phillips, On the generation of sound by supersonic turbulent shear layers, J. Fluid Mech. 9, 1 (1960).
D. Kochkov, J. A. Smith, A. Alieva, Q. Wang, M. P. Brenner, and S. Hoyer, Machine learning-accelerated computational fluid dynamics, Proc. Natl. Acad. Sci. USA 118, e2101784118 (2021).
R. D. Sandberg, and V. Michelassi, Fluid dynamics of axial turbomachinery: Blade- and stage-level simulations and models, Annu. Rev. Fluid Mech. 54, 255 (2022).
C. Lagemann, K. Lagemann, S. Mukherjee, and W. Schröder, Deep recurrent optical flow learning for particle image velocimetry data, Nat. Mach. Intell. 3, 641 (2021).
P. M. Danehy, R. A. Burns, D. T. Reese, J. E. Retter, and S. P. Kearney, FLEET velocimetry for aerodynamics, Annu. Rev. Fluid Mech. 54, 525 (2022).
M. J. Lighthill, in Viscosity effects in sound waves of finite amplitude: Surveys in Mechanics, edited by G. K. Batchelor, and R. M. Davies (Cambridge University Press, Cambridge, 1956), pp. 250–351.
L. S. G. Kovásznay, Turbulence in supersonic flow, J. Aeronaut. Sci. 20, 657 (1953).
C. J. Chapman, High Speed Flow (Cambridge University Press, Cambridge, 2000).
M. Wang, J. B. Freund, and S. K. Lele, Computational prediction of flow-generated sound, Annu. Rev. Fluid Mech. 38, 483 (2006).
G. M. Lilley, On the noise from jets, Noise Mechanisms AGARD-CP-131, 13.1–13.12 (1974).
T. Colonius, S. K. Lele, and P. Moin, Sound generation in a mixing layer, J. Fluid Mech. 330, 375 (1997).
M. E. Goldstein, An exact form of Lilley’s equation with a velocity quadrupole/temperature dipole source term, J. Fluid Mech. 443, 231 (2001).
M. E. Goldstein, A generalized acoustic analogy, J. Fluid Mech. 488, 315 (2003).
M. E. Goldstein, On identifying the true sources of aerodynamic sound, J. Fluid Mech. 526, 337 (2005).
X. Wu, Generation of sound and instability waves due to unsteady suction and injection, J. Fluid Mech. 453, 289 (2002).
D. R. Dowling, and K. G. Sabra, Acoustic remote sensing, Annu. Rev. Fluid Mech. 47, 221 (2015).
L. Q. Liu, J. Y. Zhu, and J. Z. Wu, Lift and drag in two-dimensional steady viscous and compressible flow, J. Fluid Mech. 784, 304 (2015).
L. Q. Liu, J. Z. Wu, W. D. Su, and L. L. Kang, Lift and drag in three-dimensional steady viscous and compressible flow, Phys. Fluids 29, 116105 (2017), arXiv: 1611.09615.
S. Zou, L. Liu, and J. Wu, Numerical validation and physical explanation of the universal force theory of three-dimensional steady viscous and compressible flow, Phys. Fluids 33, 036107 (2021), arXiv: 2012.11320.
A. D. Pierce, Wave equation for sound in fluids with unsteady inhomogeneous flow, J. Acoust. Soc. Am. 87, 2292 (1990).
W. Möehring, On vortex sound at low Mach number, J. Fluid Mech. 85, 685 (1978).
S. K. Lele, and J. W. Nichols, A second golden age of aeroacoustics? Phil. Trans. R. Soc. A. 372, 20130321 (2014).
R. Ewert, and J. Kreuzinger, Hydrodynamic/acoustic splitting approach with flow-acoustic feedback for universal subsonic noise computation, J. Comput. Phys. 444, 110548 (2021), arXiv: 2009.07155.
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This work was supported by the National Natural Science Foundation of China (Grant Nos. 12102365, 91752202 and 11472016). Luoqin Liu was supported by the Hundred Talents Program of the Chinese Academy of Sciences (CAS). We thank encouragement and valuable discussions from Profs. Shu-Hai Zhang, Zhan-Sen Qian, Drs. Shu-Fan Zou, An-Kang Gao, and Zhen Li.
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Mao, F., Kang, L., Liu, L. et al. A unified theory for gas dynamics and aeroacoustics in viscous compressible flows. Part I. Unbounded fluid. Acta Mech. Sin. 38, 321492 (2022). https://doi.org/10.1007/s10409-022-09033-4
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DOI: https://doi.org/10.1007/s10409-022-09033-4