Information Analysis of Relaminarizing Turbulent Boundary Layer

Abstract

An information analysis of a relaminarizing turbulent boundary layer was investigated. It has been shown by the present authors that in the free-shear turbulent transition processes, the information analysis using Shannon entropy, which focuses on the complexity of the fluctuations, was effective for a measure of the transition progress. The present study applied this information analysis to the relaminarization process of the turbulent boundary layer. The turbulent boundary layer was relaminarized by an acceleration due to flow convergence. Velocity fluctuations were measured by a hot-wire anemometer. From the probabilities of the fluctuations, the Shannon entropy was obtained. It was large near the wall, then decreased away from the wall. In addition, they rapidly decreased just after the start of the flow convergence. The rapid decrease did not appear in the turbulent statistics, e. g., the fluctuating velocity and the intermittency factor. Thus, it was found that the Shannon entropy could be a measure of the progress of relaminarization.