Numerical analysis of natural convection behavior in density stratification induced by external cooling of a containment vessel

Ishigaki, Masahiro; Abe, Satoshi; Hamdani, Ari; Hirose, Yoshiyasu

doi:10.1016/j.anucene.2021.108867

Cited by 3 publications

(3 citation statements)

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“…Kelm et al pointed out that the influence of variations of initial and boundary conditions is important and the use of accurate initial and boundary conditions is required for an accurate numerical simulation of the behavior inside a CV [1]. In addition, we revealed that the temperature boundary condition of a small internal structure in a CV has a large influence on the fluid temperature distribution [2]. Therefore, it is necessary to set the initial and boundary conditions taking into account the variations of these physical quantities.…”

Section: Introductionmentioning

confidence: 61%

“…Because carbon dioxide in the air is minimal, we ignored the effect of the thermal radiation. We simulated the natural convection behavior with the density stratification of air and helium ignoring the thermal radiation [2], and we obtained valid results. The RANS model was used, and the Reynolds-averaged equations are shown in Equations ( 1)-( 4).…”

Section: Governing Equationsmentioning

confidence: 77%

“…The numerical simulation method of fluid behavior was the same as in our previous study [2]. The numerical solver has been validated by using the results of the natural convection experiment [2] and the density stratification breakup experiment by a jet [12]. The governing equations are the mass, momentum, energy equations, and transport equations for the gas species [13].…”

Section: Governing Equationsmentioning

confidence: 99%

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Estimation of Flow Field in Natural Convection with Density Stratification by Local Ensemble Transform Kalman Filter

Ishigaki

Hirose

Abe

et al. 2022

Fluids

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For estimating thermal flow in a nuclear reactor during an accident accurately, it is important to improve the accuracy of computational fluid dynamics simulations. The temperature and flow velocity are not homogeneous and have large variations in a reactor containment vessel because of its very large volume. In addition, Kelm’s work pointed out that the influence of variations of initial and boundary conditions was important. Therefore, it is necessary to set the initial and boundary conditions taking into account the variations of these physical quantities. However, it is a difficult subject to set such complicated initial and boundary conditions. Then, we can obtain realistic initial and boundary conditions and an accurate flow field by data assimilation, and we can improve the accuracy of the simulation result. In this study, we applied data assimilation by a local ensemble transform Kalman filter to a simulation of natural convection behavior in density stratification, and we performed a twin model experiment. We succeeded in estimating the flow fields and improving the simulation accuracy by the data assimilation, even if we applied the boundary condition with error for the true condition.

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Section: Introductionmentioning

confidence: 61%

Section: Governing Equationsmentioning

confidence: 77%