Effects of non-stationarity of the flow around uniformly moving submerged body

Abstract

The paper presents estimates of the characteristics of non-stationarity of the field of flow around an ellipsoid of rotation, obtained as a result of numerical experiments with a three-dimensional non-hydrostatic model of the system “water – air”. The evolution of the structure of internal wave disturbances (in the temperature field), propagating from the ellipsoid of rotation with an elongation of 1:6, streamlined by a stream of a stratified medium with a constant velocity, was studied. Significant non-stationarity of the flow field has been identified. When flow around, wave disturbances of a complex structure are formed, the studies of which were carried out using wavelet analysis of time series at points in the vicinity of the ellipsoid and constructing integral wavelet spectra for water temperature across and along the region. In the first case, based on the comparison of the wavelet spectrum at each chosen time and integral over the entire period, a significant variability of the spectral characteristics of the water temperature field in time was demonstrated. Considering the temporal evolution of spatial integral wavelet spectra for water temperature across and along the region, the alternation of groups of wave disturbances with energy flows from small (vortex) scales to large and vice versa is clearly seen. In some periods, there is a complete destruction of the space-time pattern of perturbations. The group structure and its dynamics appear more clearly in the transverse plane above the ellipsoid.