Akintunde Akinjide, Petculescu Andi
Department of Physics, University of Louisiana at Lafayette, P.O. Box 44210, Lafayette, Louisiana 70504.
J Acoust Soc Am. 2014 Oct;136(4):1483-6. doi: 10.1121/1.4894683.
This paper presents the results of a pilot study comparing the use of continuum and non-continuum fluid dynamics to predict infrasound attenuation in the rarefied lower thermosphere. The continuum approach is embodied by the Navier-Stokes equations, while the non-continuum method is implemented via the Burnett equations [Proc. London Math. Soc. 39, 385-430 (1935); 40, 382-435 (1936)]. In the Burnett framework, the coupling between stress tensor and heat flux affects the dispersion equation, leading to an attenuation coefficient smaller than its Navier-Stokes counterpart by amounts of order 0.1 dB/km at 0.1 Hz, 10 dB/km at 1 Hz, and 100 dB/km at 10 Hz. It has been observed that many measured thermospheric arrivals are stronger than current predictions based on continuum mechanics. In this context, the consistently smaller Burnett-based absorption is cautiously encouraging.
本文介绍了一项初步研究的结果，该研究比较了使用连续介质和非连续介质流体动力学来预测稀薄低热层中的次声衰减。连续介质方法由纳维-斯托克斯方程体现，而非连续介质方法则通过伯内特方程实现[《伦敦数学学会会报》39, 385 - 430 (1935); 40, 382 - 435 (1936)]。在伯内特框架中，应力张量与热通量之间的耦合会影响色散方程，导致衰减系数比其纳维-斯托克斯对应项小，在0.1赫兹时小约0.1分贝/千米，在1赫兹时小10分贝/千米，在10赫兹时小100分贝/千米。据观察，许多实测的热层波至比基于连续介质力学的当前预测更强。在此背景下，基于伯内特方程得出的持续较小的吸收量令人谨慎地感到鼓舞。
