Change of the properties of turbulent flows in a spherical layer under the action of modulation of rotation velocity

Isothermal turbulent flows in a layer of viscous incompressible fluid confined between counter-rotating spherical boundaries have been experimentally studied. The influence of modulation of the velocity of inner sphere rotation on the characteristics of turbulence is considered. Measurements of flow velocity were carried out by laser Doppler anemometer. A local minimum is found in the dependence of the magnitude of turbulent pulsations on the amplitude of velocity modulation. It is established that, in the absence of modulation, the slopes of velocity spectra are close to –11/5. Modulation amplitude enhancing can lead to the formation of velocity spectra typical to two-dimensional turbulence, with slopes of –5/3 at low frequencies and –3 at high frequencies.