On fractal features of diffusion field in a turbulent jet.

In this short paper we present experimental results on the fractality of diffusion field of the high Schmidt number material by an axisymmetric turbulent water jet which develops into the quiescent fluid. The concentration of material has been measured by a new reflection type of optical fiber probe which has a spatial resolution of several times as large as Kolmogorov length scale. The fractal features of the measured concentration signals have been examined by the box-counting method, R/S analysis and wavelet analysis. It is found that in the central part of jet the box-dimension of sets of iso-concentration points D 1 has the values of 0.15 ≤ D 1 ≤ 0.5 and shows the significant dependency on the threshold intensity. From the R/S analysis, we found that the Hurst exponent of the concentration signal H is between 0.8 and 0.95. The wavelet analysis suggested the possibility that the concentration signal has the multifractal feature.