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Zhou, W.*; Miwa, Shuichiro*; Yamashita, Susumu; Okamoto, Koji*
Progress in Nuclear Energy, 177, p.105441_1 - 105441_17, 2024/12
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Understanding air entrainment phenomena induced by plunging water jets is critical in the fields of nuclear and hydraulic engineering. Air entrainment is one of the key safety design parameters for nuclear systems. However, most existing studies rely on empirical correlations or curve-fitting models to estimate bubble penetration depth, and no agreed-upon calculation principle exists for varying jet conditions. To address these limitations, this research developed two advanced AI approaches: an improved YOLOv5 for segmenting air entrainment and the NSGA-III-BPNN method for predicting penetration depth. The improved YOLOv5 enables real-time segmentation and extraction of air entrainment motion and dynamics under diverse conditions, demonstrating high scalability and robustness. The penetration depth estimated using the improved YOLOv5 shows greater accuracy compared to conventional empirical correlations and is more efficient than traditional image post-processing techniques for classifying shape regimes based on dynamic air entrainment patterns. To overcome the limitations of object segmentation, which typically relies on video or image data, the NSGA-III-BPNN method predicts maximum penetration depths with greater accuracy than YOLOv5, offering a more effective prediction model for air entrainment penetration depth. By leveraging advanced AI techniques, the research not only provides valuable segmentation data for refining computational fluid dynamics (CFD) modeling but also paves the way for significant advancements in both nuclear and hydraulic engineering.
Xiao, Y.*; Shen, X.*; Miwa, Shuichiro*; Sun, Haomin; Hibiki, Takashi*
Konsoryu Shimpojiumu 2018 Koen Rombunshu (Internet), 2 Pages, 2018/08
In order to develop constitutive equations of two-fluid model in rod bundle flow channels, experiments of adiabatic air-water upward two-phase flow in 6
6 rod bundle flow channel were performed. Local flow parameters such as void fraction, interfacial area concentration (IAC) and so on were measured by a double-sensor optical probe. The area-averaged void fraction and IAC data were compared with the predictions from a drift-flux model and an IAC correlation.
Yamashita, Susumu; Zhou, W.*; Miwa, Shuichiro*
no journal, ,
The development of data-driven plant safety assessment methods by integrating artificial intelligence (AI) technology and thermal hydraulics has been attracting attention as a way to reduce the time cost, range of applicability to actual phenomena, and accuracy variability that are problems in developing physical models in the field of thermal hydraulics. To contribute to developing a data-driven analysis method that automatically interprets the results of CFD calculations using AI technology, training images for building an AI model were generated by analyzing water jet into a pool system using JUPITER. The analysis was conducted using the several parameters (nozzle height, jet velocity, etc). In this presentation, we will present the calculation results for building the AI model, a quantitative comparison of the penetration length with the experimental results, problems in simulating the water impingement phenomenon, and a prediction of the penetration length by machine learning.
Murata, Tetsuya*; Miwa, Shuichiro*; Sakashita, Hiroto*; Mori, Michitsugu*; Kasahara, Seiji; Yan, X.
no journal, ,
Application of a high temperature gas-cooled reactor (HTGR) for snow melting and district heating in Hokkaido was investigated. Concept design of a heat delivery system, modeling of pipes and a heat exchanger, calculation of heat supply amount from HTGR, and determination of location of the HTGRs were carried out. Sapporo and Ishikari were assumed as a heat demand district. To supply the maximum heat demand 435 MW in a year, 2 GTHTR300s, a kind of design of HTGR, were required. Though the distance from the GTHTR300 site and the heat demand district was 40 km, the temperature of the GTHTR300 waste heat was enough for the district heating. Double pipe for the heat transportation from the GTHTR300 to the district was advantageous for less heat loss and smaller excavation area. This system required 9 double pipes and more that 5000 heat exchangers.
