Numerical analysis of a parallel triple-jet of liquid-sodium in a turbulent forced convection regime

Journal article (2024)

Authors

E. Cascioli Belgian Nuclear Research Centre, ChemE/Transport Phenomena - AS
B.J. Kaaks RST/Reactor Physics and Nuclear Materials - AS
S. Keijers Belgian Nuclear Research Centre
K. Van Tichelen Belgian Nuclear Research Centre
S. Kenjeres ChemE/Transport Phenomena - AS
Research Group
ChemE/Transport Phenomena (AS) (TU Delft)
T-RANS Liquid metal Combined dynamic LES/DNS Small modular nuclear reactors Triple-jet mixing and heat transfer Turbulent forced convection
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Published Date

2024

Language

English

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Faculty

Applied Sciences

Department

ChemE/Chemical Engineering

Research Group

ChemE/Transport Phenomena

Abstract

In the present study, we have applied a combined wall-resolving dynamic Large-Eddy Simulation (LES) (for the velocity field) and Direct Numerical Simulation (DNS) (for the temperature field) approach for mixing of parallel triple-jets with different temperatures of liquid sodium in a turbulent forced convection regime. Because of the high thermal conductivity of sodium (a low-Prandtl fluid), we adopted the dynamic Smagorinsky subgrid closure for the unresolved velocity scales, while the thermal scales are fully resolved. Furthermore, the Time-dependent Reynolds-Averaged Navier-Stokes (T-RANS) approach with the high-Reynolds number variant (i.e. with the wall functions as boundary conditions along solid boundaries) of the four-equation eddy viscosity model (k−ε−kθ−εθ) was applied. The fine-mesh LES/DNS provided a close agreement with the experimental data for both velocity and temperature fields (for both first- and second-moments). In contrast, the coarse-mesh LES/DNS overestimated the turbulent kinetic energy profiles at different distances from the inlet plane. The T-RANS results confirmed a good agreement with the mean streamwise velocity and turbulent kinetic energy, as well as the mean temperature profiles. Finally, the analysis of power spectral density distributions of the temperature signal revealed that all simulation techniques captured a dominant flow frequency originating from the induced Kelvin-Helmholtz instabilities between the side and central jets. The presented combined dynamic LES/DNS approach is recommended for future simulations of the turbulent forced convection flows of low Prandtl fluids, especially if thermal fatigue effects need to be predicted correctly.