Experimental study of turbulent coherent structures under different flow mixing devices in lower plenum of a scaled-down reactor pressure vessel

• Published in: Nuclear engineering and design 2024-11, Vol.428, p.113475, Article 113475
• Main Authors: Qu, Wenhai, Wang, Hanyu, Xie, Hao, Xiong, Jinbiao
• Format: Article
• Language: English
• Subjects: Coherent structure; Flow mixing device; Reactor pressure vessel; Turbulent flow
• ISSN: 0029-5493
• DOI: 10.1016/j.nucengdes.2024.113475

•The turbulent flow was obtained with three kinds of flow mixing devices in lower plenum.•Turbulent coherent structures were extracted to study the turbulent mixing mechanism of flow mixing devices.•High-precision matched-index-of-refraction technique is employed to measure the turbulent flow in a scaled-down reactor pressure vessel. Turbulent flow mixing in lower plenum of reactor pressure vessel (RPV) of pressurized water reactor (PWR) is important for design of flow mixing devices. In this study, turbulent flow in a scaled-down RPV model with three designs of mixing devices, including vortex suppression plate, flow skirt and semi-spherical perforated drum, was measured by time-resolved particle image velocimetry (TR-PIV) with aid of the high-precision MIR technique of sodium iodide (NaI) solution and acrylic. Turbulent coherent structures were studied based on the experimental data. The time-averaged flow structures in lower plenum include flow separation at lower support plate, fluid bifurcation at the flow mixing devices, horizontal jets at holes of flow skirt, flow turning horizontally below the flow mixing devices and flow turning upward through the flow mixing devices. The strong turbulent mixing induced by flow mixing devices improves Reynolds stresses in lower plenum and introduces large spatial–temporal length scales in lower plenum.