Based on 2-D discrete Fourier transforms (DFT) of infrared images from water jet and the analyses of its 2-D spatial spectrum, investigations were made on the spatial scales of passive scalars turbulent flow in high pressure water jet fields, which are represented by infrared images. The characteristic length scales and the law of their temporal evolution process were obtained in the energy (or convection) range, the dissipation range and the inertial range in between. Based on 1-D DFT, the turbulent temporal fluctuation characteristics were obtained for the interest points at large scale eddy center in convection range, sub-scale eddy center in inertial range, dissipation range, as well as in the axis of the jetting flow. In addition, the fractal dimensions were also calculated upon the 1-D spectrum, which was then used for fractal characterization of temporal fluctuations of the interest points in different scale regions of the scalars turbulent flow.
Gong Weili, Zhao Haiyan, An Liqian, Mao Lingtao.Temporal and spatial analysis of infrared images from water jet in frequency domain based on DFT[J] JOURNAL OF BEIJING UNIVERSITY OF AERONAUTICS AND A, 2008,V34(06): 690-694