重力波波包在时变背景场中传播的数值研究

采用二阶算子分裂格式对高斯型重力波波包在时变背景温场和时变背景风场中的非线性传播过程分别进行了数值模拟和分析．研究表明,时变背景场对波包空间结构演变影响不明显,各物理量的偏振关系与线性理论偏振关系较一致;在时变背景温场中传播,水平群速度和垂直群速度的变化趋势与线性理论结果相反,波频率的变化也与线性理论色散方程计算结果有一定的差别,这表明了线性重力波理论的局限性;在时变背景风场中传播,波频率的变化比时变背景温场中更显著．传播路径与在稳恒背景场中比较,更接近线性理论计算出的路径．

Numerical Study on the Propagation of Gravity-Wave Packet in Time-Variant Background Fields

By using 2nd order operator-splitting scheme,numerical simulations of nonlinear propagation for a Gaussian gravity-wave packet in time-variant background temperature and wind fields are carried out individually. The simulation results show that the time-variant background fields influence little on the spacial structure of the wave packet, and the polarization relations of each wave disturbance components agree well with that of the linear gravity wave theory. Propagating in a time-variant background temperature field, the propagation paths of the gravity-wave packet are obviously different from the paths derived from the linear wave theory, and the variational tendency of the horizontal and vertical group-velocities are opposite to prediction of the linear theory, and a little difference is found in the variation of wave frequency between the simulation result and the dispersion relation of gravity wave.These indicate that the linear wave theory isn't feasible to describe quantitatively the nonlinear propagation of the gravity wave packet in time-variant background fields. While in a time-variant background wind field, the background impacts more significantly on the wave frequency than in time-variant background temperature field, and the propagation paths is more close to the paths of the linear theory than that in a steady-state background field.