Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 12, 2022 - November 13, 2022
An information analysis using permutation entropy of was applied to a relaminarizing sink flow turbulent boundary layer. The turbulent boundary layer was relaminarized by an acceleration because of the contraction of the flow area. It has been shown by the present authors that laminar-turbulent transition processes in the free-shear flow, the permutation entropy was effective for a measure of the transition progress. Velocity fluctuations were measured by a hot-wire anemometer. From the time series of the fluctuations, the permutation pattern of the data increase or decrease was discriminated, then the entropy based on the probability of the pattern was obtained. The permutation entropy did not decrease with the progress of the relaminarization. Therefore, it is hard to be an appropriate measure of the progress. It increased at the outer edge of the boundary layer. The two factors contributed it. One was an increase of number of permutation patterns, the other was an equalization of the permutation pattern probabilities. Both factors were affected by the intermittent fluctuations there. When the number of extracted data matched the Kolmogorov timescale, the permutation entropy took a large constant value near the wall in the boundary layer because of extremely large number of the extracted data.
