球周辺のプルーム拡散場の統計的特性について

概要

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This paper is the second one by the authors, which clarifies the effects of flow distortion by a sphere upon the statistics of a point-source diffusing plume evolved in grid-generated turbulence. In the preceding paper, only the results on the forward stagnation streamline was given. Here, various statistics of the whole concentration field around the sphere are investigated. It is found that the conditioned mean concentration has almost the same level everywhere but in the wake recirculation region, but the conditioned concentration fluctuation rms values show a slight drop near the surface of the sphere in the non-recirculation flow region. And, except for the wake recirculation region, the conditioned probability density for near-zero concentration shows slight drop, while that for the higher concentration increases slightly as the sphere is approached. Furthermore, from the spectra, the intermittency and the probability density distribution, it is rationally concluded that only in the region next to the surface of the sphere, has the molecular diffusion fully advanced and the concentration fluctuation dropped to nearly zero.
1992-01-25