Transitional Intermittency Exponents Through Deterministic Boundary-Layer Structures and Empirical Entropic Indices

Entropy

关键词: boundary layer flows;    deterministic structures;    empirical entropy;    empirical entropic index;    intermittency exponent;   

DOI  :  10.3390/e16052729

来源: mdpi

【 摘 要 】

A computational procedure is developed to determine initial instabilities within a three-dimensional laminar boundary layer and to follow these instabilities in the streamwise direction through to the resulting intermittency exponents within a fully developed turbulent flow. The fluctuating velocity wave vector component equations are arranged into a Lorenz-type system of equations. The nonlinear time series solution of these equations at the fifth station downstream of the initial instabilities indicates a sequential outward burst process, while the results for the eleventh station predict a strong sequential inward sweep process. The results for the thirteenth station indicate a return to the original instability autogeneration process. The nonlinear time series solutions indicate regions of order and disorder within the solutions. Empirical entropies are defined from decomposition modes obtained from singular value decomposition techniques applied to the nonlinear time series solutions. Empirical entropic indices are obtained from the empirical entropies for two streamwise stations. The intermittency exponents are then obtained from the entropic indices for these streamwise stations that indicate the burst and autogeneration processes.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland