Abstract
In order to investigate the characteristics of the lee waves, numerical experiments are performed by integrating the equations of the so-called Boussinesq system as an initial value problem for a given topography with rigid upper boundary. Some considerations on the linear theory are presented for a better understanding of the results. For almost all internal Froude number Fi, a quasi-steady pattern is obtained. Calculated patterns are discussed in connection with the linear theory, and good agreements are obtained. For relatively large values of the Fi, a laminar sinusoidal flow is obtained. On the other hand for small values of the Fi, a S-shaped or Rotor-like flow pattern is obtained, in which a statically unstable region is found to survive. Such a flow may be considered as a result of a nonlinear interference of the waves. Occurrence of such an overturning flow also depends on the height of the mountain. The criterion for the overturning flow seems to be linear dependency in terms of the nondimensional mountain height D and Fi, which appears to be consistent with Long's analytical study (1955).
Strong lee-side surface winds are discussed in relation to the simulated lee waves. The possibility of a strong downslope wind or horizontal wind at the lee side of the mountain is stressed.
