Daniele Dovizio , Boshen Bian , Walter Villanueva , Ed Komen
{"title":"Validation of CFD RANS of an internally heated natural convection in a hemispherical geometry","authors":"Daniele Dovizio , Boshen Bian , Walter Villanueva , Ed Komen","doi":"10.1016/j.nucengdes.2024.113471","DOIUrl":null,"url":null,"abstract":"<div><p>In the context of severe accidents, one mitigation strategy that has been shown to work for low-to-intermediate power reactors is the In-Vessel Melt Retention (IVMR) of molten corium. For this reason, several efforts have been put forward to make this strategy feasible for high power reactors. In particular, the aim of the European H2020 IVMR project was to evaluate and improve current modeling strategies, such as the use of Computational Fluid Dynamics (CFD) codes for the prediction of flow and heat transfer in a homogeneous corium pool. Due to evident limitations, the validation was mainly performed against an available water-based experimental data, rather than a corium mixture. In order to overcome this limitation, complementary high fidelity numerical simulations, in the form of Direct Numerical Simulation (DNS), have been performed recently and are used in the current work as a reference for the validation purposes of the Reynolds Averaged Navier–Stokes (RANS) approach. More specifically, RANS numerical simulations of a three-dimensional hemispherical configuration are performed using the STAR-CCM+ software. Consistent with the DNS approach, the Boussinesq assumption is used to characterize the internally heated (IH) natural convection problem. The flow conditions correspond to a Rayleigh number of <span><math><mrow><mn>1</mn><mo>.</mo><mn>6</mn><mi>⋅</mi><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>11</mn></mrow></msup></mrow></math></span> and a Prandtl number of 0.5. Several turbulence models available in STAR-CCM+, which are generally used for buoyancy driven flows, are compared and evaluated against the DNS results, in terms of velocity, temperature, buoyancy production of the turbulent kinetic energy and heat flux. Reasonable results are obtained by the RANS models, especially in predicting the main qualitative features of the flow configuration, such as thermal stratification, fast descending flow on the curved walls and high turbulence at the top of the domain. The main divergence between RANS and DNS is observed in the bulk region, where all the RANS computations present strong recirculation, while an extended nearly stagnant zone is predicted by DNS calculations. A quantitative analysis is performed as well, highlighting the limitations of the RANS approaches, especially for the turbulent heat flux modeling, and the need for the development of more advanced models as potential future efforts.</p></div>","PeriodicalId":19170,"journal":{"name":"Nuclear Engineering and Design","volume":"428 ","pages":"Article 113471"},"PeriodicalIF":1.9000,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Nuclear Engineering and Design","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0029549324005715","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"NUCLEAR SCIENCE & TECHNOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
In the context of severe accidents, one mitigation strategy that has been shown to work for low-to-intermediate power reactors is the In-Vessel Melt Retention (IVMR) of molten corium. For this reason, several efforts have been put forward to make this strategy feasible for high power reactors. In particular, the aim of the European H2020 IVMR project was to evaluate and improve current modeling strategies, such as the use of Computational Fluid Dynamics (CFD) codes for the prediction of flow and heat transfer in a homogeneous corium pool. Due to evident limitations, the validation was mainly performed against an available water-based experimental data, rather than a corium mixture. In order to overcome this limitation, complementary high fidelity numerical simulations, in the form of Direct Numerical Simulation (DNS), have been performed recently and are used in the current work as a reference for the validation purposes of the Reynolds Averaged Navier–Stokes (RANS) approach. More specifically, RANS numerical simulations of a three-dimensional hemispherical configuration are performed using the STAR-CCM+ software. Consistent with the DNS approach, the Boussinesq assumption is used to characterize the internally heated (IH) natural convection problem. The flow conditions correspond to a Rayleigh number of and a Prandtl number of 0.5. Several turbulence models available in STAR-CCM+, which are generally used for buoyancy driven flows, are compared and evaluated against the DNS results, in terms of velocity, temperature, buoyancy production of the turbulent kinetic energy and heat flux. Reasonable results are obtained by the RANS models, especially in predicting the main qualitative features of the flow configuration, such as thermal stratification, fast descending flow on the curved walls and high turbulence at the top of the domain. The main divergence between RANS and DNS is observed in the bulk region, where all the RANS computations present strong recirculation, while an extended nearly stagnant zone is predicted by DNS calculations. A quantitative analysis is performed as well, highlighting the limitations of the RANS approaches, especially for the turbulent heat flux modeling, and the need for the development of more advanced models as potential future efforts.
期刊介绍:
Nuclear Engineering and Design covers the wide range of disciplines involved in the engineering, design, safety and construction of nuclear fission reactors. The Editors welcome papers both on applied and innovative aspects and developments in nuclear science and technology.
Fundamentals of Reactor Design include:
• Thermal-Hydraulics and Core Physics
• Safety Analysis, Risk Assessment (PSA)
• Structural and Mechanical Engineering
• Materials Science
• Fuel Behavior and Design
• Structural Plant Design
• Engineering of Reactor Components
• Experiments
Aspects beyond fundamentals of Reactor Design covered:
• Accident Mitigation Measures
• Reactor Control Systems
• Licensing Issues
• Safeguard Engineering
• Economy of Plants
• Reprocessing / Waste Disposal
• Applications of Nuclear Energy
• Maintenance
• Decommissioning
Papers on new reactor ideas and developments (Generation IV reactors) such as inherently safe modular HTRs, High Performance LWRs/HWRs and LMFBs/GFR will be considered; Actinide Burners, Accelerator Driven Systems, Energy Amplifiers and other special designs of power and research reactors and their applications are also encouraged.