旋回乱流の時空間3重相関に関する基礎研究

概要

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Measurements have been made for space-time correlation, i. e. triple velocity correlations with both spatial separation and time delay in the turbulent shear flow around a circular cylinder spinning in a quiescent fluid. The integral macro time scales of triple correlations S_<2.2> and S_<12.2> are about a half that for double correlation Q_<2.2>. The validity of Taylor's hypothesis of frozen turbulence is examined for triple correlations. The data show that this hypothesis is valid except for the region near the wall as in the case of a flat plate-boundary layer. The spatial structure of the turbulence fields is inquired by using various contour maps of the spatial iso-correlation in the various cross sections. The extent of iso-correlation maps for S_<2.22> and S_<12.2> in the rs-φs cross section is a qurter that in the Q_<2.2>. Iso-correlation maps for S_<2.32> in the ys-φs and ys-rs cross sections show rather anti-symmetry with respect line of φs=0.
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