Clarification of flow scale dependency of mass transfer in high Schmidt nunmber turbulent flow and challenge for pipe wall thinning control technique

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06952
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Nuclear engineering
• Research Institution: Tohoku University
• Principal Investigator: Shinji Ebara 東北大学, 工学研究科, 准教授 (30325485)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 配管減肉 / 流れ加速型腐食 / 流れの可視化実験 / 濃度場可視化実験 / PIV / LIF / 周波数解析

Outline of Final Research Achievements

In this study, an accelerated wall thinning experiment using benzoic acid as thinning wall, flow visualization experiment by means of PIV and visualization experiment of concentration field using LIF were conducted in order to analyze mass transfer from a channel wall in a complex high Schmidt number turbulent flow downstream of an orifice. From the observation of the concentration field, it was found that frequent and intermittent ejections of high concentration fluid from a channel wall appeared in large wall thinning rate area. The ejections instantaneously reached up to several mm in height whereas the viscous sublayer thickness was assumed to be of the order of 0.1 mm and the concentration boundary layer thickness was assumed to be thinner than it in the area. This phenomena observed is considered to indicate that larger vortex structures than the viscous sublayer and concentration layer have a lot to do with the mass transport from the channel wall.

Free Research Field

原子力工学、核融合炉工学

Academic Significance and Societal Importance of the Research Achievements

本研究では、各種プラントなどで生じる配管減肉の中の流れ加速型腐食について、その流動因子がレイノルズ応力も含めた全剪断応力にあることを明らかとした。しかも、壁面で生じる減肉現象に対して、壁面直近ではなく壁面から数㎜離れた位置における全剪断応力が影響しているという結果が得られた。乱流物質伝達の研究は種々行われているが、オリフィス下流という複雑体系においては詳細な計測を行ったものは少ないため、本研究で大きな成果が得られたと言える。