流動加速腐食による配管減肉に関する研究（旋回流とオリフィス偏心の組み合わせ効果による非対称流の発生）

概要

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The flow accelerated corrosion in a pipe is an important topic of interest associated with pipe-wall thinning phenomenon in a highly aged nuclear power plant. In the present study, the velocity field behind an orifice in a pipe is studied by PIV measurement in some combinations of swirl flow magnitudes and orifice bias. The flow observations along the flow axis and across the pipe indicate that the effect of orifice bias is not so influential on the flow behavior behind the orifice at small swirl flow magnitude. However, the asymmetrical flow pattern is observed in the flow behind the orifice at large swirl flow magnitude. The accelerated flow behind the orifice reattaches on the pipe wall of shorter orifice height and the corresponding velocity fluctuation decreases at large swirl flow magnitude, which occurs even at the small orifice bias of 0.7% of pipe diameter. This phenomenon is expected to promote the asymmetrical distribution of pipe-wall thickness due to flow accelerated corrosion in a prototype pipe flow.