Application of Some Turbulence Models to Simulate Buoyancy-Driven Flow

Abstract

During a severe nuclear power plant (NPP) accident, large amounts of hydrogen and steam can be produced in nuclear reactor containment. In the case of hydrogen combustion, there is a possibility of producing short term pressure or detonation force. Therefore, these gas species’ production could threaten containment integrity. For instance, in the past, two gas explosion accidents occurred: In 1979 Three Mile Island and in 2011 Fukushima. After these accidents, modeling the gas behavior became an important topic in nuclear safety analyses. In order to predict hydrogen behavior and other gas species transport, mixing and combustion, reliable turbulence models need to be applied. In this work, standard k–ε, k–ω, RNG k–ε, Realizable k–ε and SST k–ω turbulence models are addressed. The computations are performed with HYDRAGON code. HYDRAGON code is a three-dimensional thermal-hydraulic code, developed to solve low-speed gas flow of compressible Navier-Stokes equations in cartesian or cylindrical coordinates or a mixture of the two coordinates. The goal of this work is to test the performance of these models by comparing the results to the benchmark. The code aims to predict containment thermal-hydraulic conditions during NPP accident.

Sensitivity Analysis of Some Key Factors on Turbulence Models for Hydrogen Diffusion Using HYDRAGON Code

“…The vaule of turbulent Prandtl number was kept as 0.9. The Standard k − ε turbulence model (Abdalla et al, 2014;Saeed et al, 2016) Eddy viscosity:…”

“…The model constants determined from simple benchmark are C u = 0.0, σ k = 1.0, Pr = 0.85, C ε1 = 1.44, C ε2 = 1.92, σ ε = 1.3 The Realizable k − ε model equations are (Abdalla et al, 2014;Saeed et al, 2016). Transport equations of the RLZ turbulence model:…”

“…The possible risk related to hydrogen was initially observed during the accident which occurred in Three Mile Island (TMI) in 1979. This was the first well-known example where combustion of hydrogen took place, and where an enormous quantity of hydrogen was generated as a consequence of steam-zirconium interaction in the fuel cladding (Abdalla et al, 2014;Saeed et al, 2016Saeed et al, , 2017aHuanga et al, 2017). The hydrogen detonation in the Fukushima Dai-ichi Nuclear Power Plant (NPP) accident (2011) was another example which compelled scientists to explore the risk of hydrogen detonation during a severe accident.…”