J0101-1-2 Quantitative Representation of Laminar-Turbulent Transition in Boundary Layer Flow Using Data Compression

Abstract

In order to indicate the complexity of signals in turbulent flows quantitatively, we used a concept of Kolmogorov complexity in computational science. The velocity data was compressed with the use of software for compression. The ratio of data size after compressed one to original one reflects the complexity of the data. Thus we named the ratio "Approximated Kolmogorov Complexity". The present analysis was applied to the laminar-turbulent transition process in a boundary layer and compared with the intermittency factor. At turbulent region, the intermittency factor became unity near the wall. On the other hand, the approximated Kolmogorov complexity had a rather smaller value than at y/δ ≒ 0.05. This tendency suggested an existence of the coherent structure of turbulent boundary layer.