乱流境界層における大規模構造間の剪断層がバースト現象に及ぼす影響

抄録

In this study, the effect of the shear layer existing between large-scale motions (LSMs) on bursting phenomenon in turbulent boundary layer (TBL) was investigated by wind tunnel experiment. The TBL was generated on the flat plate made of Bakelite with a zero pressure gradient. The Reynolds number based on friction velocity given by Re_τ = u_τδ/ν is about 1260. A self-made multi-point hot-wire probe consisting of a hot-wire Rake and a single I-type hot-wire probe was adopted. The hot-wire Rake was used to extract the LSMs from the fluctuation velocity distribution in the log-region in TBL. And the shear layer was considered to exist between the positive large-scale motion (pLSM) and the negative large-scale motion (nLSM). The bursting phenomenon was detected by VITA technique from the fluctuation velocity measured by the single I-type hot-wire probe installed under the center of the Rake in the buffer layer in the TBL. To evaluate the effect of the shear layer on bursting phenomenon, the bursting frequency under several different conditions was calculated. It was found that the bursting frequency has increased 20% with the existence of the shear layer. A further investigation showed that these increased bursting phenomena were related to the leg of the hairpin vortex.