Abstract

We have experimentally investigated turbulent flow in an elbow in order to establish a model for the vibrations excited by turbulence. Velocities were measured in a piping system with an elbow. The test section consisted of straight pipes with a single 90° elbow.

Measurements of flow velocity distribution and intensity of turbulence were carried out in the region Re = 1 × 105 ∼ 3 × 105. The measurements were performed in cross sections 1D ∼ 4D down an exit of an elbow by laser Doppler velocimetry. Each cross section had 37 measurement points.

We compared the axial velocity distribution with the turbulence intensity. The larger the turbulence intensity was, the higher the mean velocity was. Also the turbulence intensity was related to the spatial gradient of the mean velocity. Both the effects of mean velocity and its spatial gradient were dominant in the mechanism of turbulence production.

As a result of this study, the authors compiled a database on the turbulence excitation source of an elbow pipe and obtained a hypothesis on the relationship between mean velocity distribution and vibration sources. Both the database and the hypothesis are presented in this paper.

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