Научный вестник МГТУ ГА (Oct 2018)
A validity of phenomenological models of turbulence in experimental studies
Abstract
Estimates of the velocity of the chaotic medium motion using information of "narrow" spectral intervals of stationary random signals generated by the motion of such media on the sensors located at two points along the direction of medium motion are considered. The question about the physical meaning of the minimum spectral interval required for such measurements with a given accuracy is posed and discussed based on the main relations given in the article and formulated using the theory of homogeneous isotropic turbulence. It is shown, that within suggested relations the process of filtration may be described using a turbulent term and so the results of the filtration could be seen as a virtual turbulent dissipation. The latter allowed semiquantitatively describing the results of the numeric calculations presented in the article and forming the ways of the further development of the approach suggested which after appropriate updating might be called a "full filtered correlation analysis" (FFCA). In particular, a method of turbulent dissipation rate measurement by means of two (or more) filters with different bandpasses applied to signals in two points of cross-correlation measurements and an approach to the physically clear description of the optimal number of Fourier-terms in the representation of the signal passed the filter are outlined as well as the approach to a turbulence spectral shape evaluation. Apart from that, with the relations given in the article, the well-known fact that Doppler measurements are not applicable to the remote sensing with use of wideband signals as an information carrier as well as the reason why such measurements are applicable in the case of signals with narrow spectra receive its clear physical explanation. The latter allows forming the definition of a monochromatic signal as it is from the point of view of a cross-correlation analysis.
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