Study on Miter-Bend Flow : Part 6-Velocity Distribution in Turbulent Flow and Influence of Length of Upstream Conduit upon Flow Pattern in Laminar Flow

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  • 屈折管内の流れに関する研究 : 第6報-乱流における流速分布および層流における流動様相に及ぼす上流側管路長さの影響
  • 屈折管内の流れに関する研究-6-乱流における流速分布および層流における流動様相に及ぼす上流側管路長さの影響
  • クッセツカンナイ ノ ナガレ ニカンスルケンキュウ 6 ランリュウ ニ オケル

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Abstract

In this paper following the previous ones, some aspects of the flow patterns of the miter-bends with different bending angles Θ's and areal ratios λ's in laminar and turbulent flow are reported. The miter-bends under experiment have rectangular cross-sections. First, the velocity distributions were measured in turbulent flow. The velocity distributions in the center-line plane of the miter-bend change more severely in the neighbourhood of the bending part than those in the plane perpendicular to the center-line plane independently of Θ and λ. Generally, the variations in velocity distribution measured in the center-line plane increase with the increase of Θ when λ remains constant and with the decrease of λ when Θ remains constant. The variations in velocity distribution due to the presence of the miter-bend persist broader in the downstream section of the miter-bend than those in the upstream section. In the downstream section they extend further downstream than the variations in static pressure distribution due to the presence of the miter-bend. The measured velocity distributions in the center-line plane of the miter-bend in the neighbourhood of the bending part coincide fairly well with the computed results obtained by the analysis based upon the two-dimensional potential theory with separation at the convex corner, and further they coincide qualitatively with the results obtained by the numerical analysis in two-dimensional laminar flow. Next, in laminar flow, in order to clarify the relation between the variation of the length of the upstream conduit l_<10>/h_1 and the flow pattern, the experiments were made on the miter-bends with rectangular cross-sections and with the nozzles at the end of the upstream conduit. The flow patterns in the upstream conduit are influenced more remarkably by the change of l_<10>/h_1 than that in the downstream conduit. The flow mechanisms are considered together with the results obtained by the numerical analysis. The measured separation points of laminar boundary layer developing on the walls upstream of the concave corner are compared with the results obtained by the analytical method.

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