ИСТИНА

Цель работы - исследование возможности подавления неустойчивости и турбулентности в течениях с вращением за счет воздействия широкополосного шума с контролируемой интенсивностью и видом спектра.

The aim of the proposed project is a comprehensive experimental and numerical study of possible ways to suppress instability and turbulence in three-dimensional flows of viscous incompressible fluid in rotating spherical layers. The results obtained in the project can be used in the development of new and improvement of known technological processes (forexample, in the technology of separation of materials, in the technology of energy extraction from low-speed wind and wave flows, in the technology of processing of liquid metals and melts, as well as the growth of monocrystals). The project participants have previously received a patent for the invention "Method for eliminating turbulence in flows with rotation" (RU 26766834 C1, 2019). In this invention, periodic in time oscillations of the rotational velocity of one of the layer boundaries with controlled frequency and amplitude were used as the controlling action necessary to eliminate turbulence and transition to laminar flow states. The same type of control actions, as established by the project participants, can also be used to suppress instability. But it was found that the effectiveness of suppression of unstable and turbulent states of viscous incompressible fluid flow at such types of actions strongly depends on the frequency. The scientific novelty of the proposed project is that the susceptibility of unstable and turbulent states of flows to the effects of broadband noise external to the flows will be investigated. The study of noise propagation in the flows, namely the evolution of the properties of broadband fluctuations with removal from the noise source, is also a scientific advance. As a control action to suppress instability and/or turbulence in three-dimensional flows with rotation it is proposed to use low-amplitude "white" noise (the spectrum of such noise is uniform throughout the frequency band) with a controlled level of pulsations. It is possible that in some cases, flows may be more receptive to the effects of broadband fluctuations than to the effects of monochromatic fluctuations. Sources of noise can be random in time fluctuations of the rotation speed of one of the layer boundaries. The project participants worked out the process of introducing the above-mentioned type of noise into the flows, both in the experiment and in direct numerical simulations. Recent research results obtained by the project participants have shown that even very weak changes in the intensity of low-amplitude noise can affect the flow. The introduction of additional noise can lead, for example, to an increase in the average flow velocity, as well as to a change in the wave numbers after the instability. The process of spreading and changing the type of spectrum of broadband random fluctuations in flows of various kinds has not yet been studied sufficiently, and the results of research in this area are not only of undoubted scientific interest, but may also be useful in some applications, for example in creating new methods of detection and/or control of the intensity of broadband noise sources. The results obtained in the execution of the proposed project can be used in the development of new technical systems and industrial technologies.