Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 08, 2021 - November 10, 2021
The complexity or randomness of the relaminarization process of an accelerated turbulent boundary layer was analyzed by use of Kolmogorov complexity. Velocity data from a hot-wire anemometer was compressed using a compression program running on a Windows PC. From the compressed data, the approximated Kolmogorov complexity, named AK, and normalized compression distance, NCD was obtained. The values of AK of fluctuating velocity, time derivative of fluctuating velocity, and squared time derivative of fluctuating velocity, decreased toward downstream. Therefore, it was found that the relaminarization process can be properly represented. During the relaminarization process, the distribution of AK differs between streamwise and wall-normal fluctuating velocities, which can be explained by the difference of distribution of the fluctuating velocity themselves. On the other hand, some aspects are different from the fluctuating velocity themselves. AK shows different distributions among fluctuating velocity, time derivative of fluctuating velocity, and squared time derivative of fluctuating velocity. In particular, the turbulent structure of the relaminarization process could be clarified in more detail by comparing the AK of the squared time derivative of fluctuating velocity, with turbulent energy dissipation. From the NCD of streamwise fluctuating velocity whose reference position is within turbulent region, the turbulent structure appeared to turn into different one. Therefore, by changing the reference position of NCD, we were able to capture important changes that do not appear in the turbulent statistics.
