【摘要】 本文从可压缩情况下的流体力学方程出发,采用多重尺度方法和W.K.B.方法,研究时空变化风场中声重波波包的演变过程。文中导出了声重波波长、相速、传播方向以及振幅的演变方程。结果表明,沿群路径上波长、相速和传播方向的变化取决于风场的时空变化以及风场与波的相对方位。此外,波振幅的演变方程还表明:在时空慢变风场中,声重波的波作用量具有守恒性,声重波波包能量增加伴随波频率增高,声重波波包能量减小伴随频率降低。能量变化的实质是,风场的时变性引起了波流相互作用。更多还原

【Abstract】 Starting from the compressible hydrodynamic equations and using multiple scale method and W. K. B. method, we have investigated the evolution process of an AGW packet in a spatially and temporally varying wind. The evolution equations of wavelength, phase velocity, propagation direction and amplitude of the AGW packet are derived. It is shown that the variations of the wavelength, phase velocity and propagation direction depend on the spatial and temporal variation of the wind and also on the direction of the wave packet with respect to the wind. By analyzing the evolution equation of the amplitude, we found that the wave action of AGW is conserved in the spatially and temporally slowly varying wind. Further analysis shows that an increase of the packet energy is accompanied by an increase of the wave frequency, while a decrease of the packet energy is accompanied by a decrease of the wave frequency. The cause of the packet energy variation is wave-flow interaction produced by temporal variation of the wind.更多还原