再層流化する乱流境界層における時空間構造の複雑さ解析

抄録

The complexity or randomness of the relaminarization process of an accelerated turbulent boundary layer was analyzed by use of Kolmogorov complexity. Streamwise fluctuating velocity was measured at two points separated in the spanwise direction. The velocity was measured by two single hot-wire probes simultaneously. Velocity data 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. AK of two-point velocity difference increased as the spatial separation increased. The similarity of velocity between the two points affected this result. AK of two-point velocity difference decreased downstream due to the relaminarization. NCD between the two-points velocity was large when both velocity data are within turbulent flow because of the dissimilarity between both turbulent data. The behavior of NCD between two-point velocity difference corresponded to the velocity difference itself. From the NCD also, the relaminarization was confirmed.