Study on Miter-Bend Flow : Part 3-Observation of Flow Pattern

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  • 屈折管内の流れに関する研究 : 第3報-流動様相の観察
  • 屈折管内の流れに関する研究-3-流動様相の観察
  • クッセツカンナイ ノ ナガレ ニカンスルケンキュウ 3 リュウドウ ヨウソウ

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Abstract

In Part 1 and 2, studies were made on various miterbends with different bending angles and crosssectional areal ratios, and considerations were made on the mechanisms of pressure loss in real miter-bends by using the analytical and computed results of flow including separation at the convex corner, which are based on two-dimensional potential theory. As a result, it was reported that the detailed clarification of the complicated aspects of flow in real miter-bends such as a secondary flow, separation, reattachment, etc. is very important to industry. So, first in this report, the authors minutely observed flow patterns in miter-bends in laminar flow and compared computed and observed results of streamlines and the separation point on the wall upstream of the concave corner. Next, they measured pressure distributions of miter-bends, which were situated within the inlet length, in turbulent flow, and then showed the relation among the separation point on the wall upstream of the concave corner, bending angles, crosssectional areal ratios and Reynolds numbers. These measured results are compared with computed results. The obtained results are summarized as follows. First, in laminar flow: 1) It is shown by the observations of streamline flow patterns that flows in miter-bends are very complicated including separation, reattachment, eddy region formed by reversed flow, and a secondary flow. 2) The authors compared the computed and experimental results of streamlines in two-dimensional potential flow and of the separation point on the wall upstream of the concave corner, and both results agreed fairly well. Next, in turbulent flow: 3) The measured results of pressure distributions and the results observed by using flow visualization method show that flow patterns in miter-bends in turbulent flow are similar to those in laminar flow. 4) The separation point on the wall upstream of the concave corner is computed and compared with the experimental results. Both results coincide fairly well when the section upstream of the concave corner is long and the Reynolds number is large.

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