Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Assessment of turbulent heat flux models for URANS simulations of turbulent buoyant flows in ROCOM tests

  • Received : 2021.12.20
  • Accepted : 2022.07.16
  • Published : 2022.11.25
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Abstract

Turbulent mixing in buoyant flows is an essential mechanism involved in many scenarios related to nuclear safety in nuclear power plants. Comprehensive understanding and accurate predictions of turbulent buoyant flows in the reactor are of crucial importance, due to the function of mitigating the potential detrimental consequences during postulated accidents. The present study uses URANS methodology to investigate the buoyancy-influenced flows in the reactor pressure vessel under the main steam line break accident scenarios. With a particular focus on the influence of turbulent heat flux closure models, various combinations of two turbulence models and three turbulent heat flux models are utilized for the numerical simulations of three ROCOM tests which have different characteristic features in terms of the flow rate and fluid density difference between loops. The simulation results are compared with experimental measurements of the so-called mixing scalar in the downcomer and at the core inlet. The study shows that the anisotropic turbulent heat flux models are able to improve the accuracy of the predictions under conditions of strong buoyancy whilst in the weak buoyancy case, a major role is played by the selected turbulence models with essentially a negligible influence of the turbulent heat flux closure models.

Keywords

Acknowledgement

This research was conducted within the frame work of the Steady-State, Transient and Radiation Safety Analyses (STARS) program at PSI. The authors would like to acknowledge China Scholarship Council (CSC) for the financial support.

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