Kolmogorov Theory of Turbulence SPIE（柯尔莫哥洛夫湍流理论方法相比）.pdfVIP

6 Atmospheric Optics Kolmogorov Theory of Turbulence Classical studies of turbulence were concerned with fluctuations in the velocity field of a viscous fluid. In particular, it was observed that the longitudinal wind velocity associated with the turbulent atmosphere fluctuates randomly about its mean value. That is, the wind velocity field assumes the nature of a random or stochastic field, which means that at each point in space and time within the flow the velocity may be repre- sented by a random variable. A statistical approach has been fruitful over the years in describing both atmospheric turbulence and its various effects on optical/IR systems. For the purpose of mathematical simplifi- cation, it is often necessary in such statistical approaches to assume that point separations within certain scale sizes exhibit the important characteristics of statistical homogeneity and isotropy. In general, statistical homogeneity of the random velocity field implies that the mean value of the field is constant and that correlations between random fluctuations in the field from point to point are independent of the chosen observation points, depending only on their vector separation. Moreover, if the random fluctuations are also statistically isotropic, then point-to-point correlations depend only on the magnitude of the vector separation between observation points. Kolmogorov Theory of Turbulence 7 Classical Turbulence Classical turbulence is associated with the random velocity fluctuations of a viscous fluid such as the Energy injection atmosphere. The atmo- sphere has two distinct states of motion: lamin