# Verification and validation in LES of triple parallel jet flow for a thermal striping investigation

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Abstract : Large Eddy Simulation (LES) consists in explicitly resolving the largest turbulent scales while thesmall-scale motions are taken into account by means of a subgrid-scale (SGS) model. Although itremains computationally expensive, LES seems to constitute an increasingly employed tool forengineering applications in fluid mechanics. In a nuclear context e.g., LES is a relevant approach for the numerical study and prediction of the thermal striping, which can occur during the functioning of sodium-cooled nuclear reactors and may cause some damage to the structures. Numerous experiments where three differentially heated jets mix inside a cavity were designed and conducted by the Japan Atomic Energy Agency for studying these phenomena. In order to evaluate the quality of LES using the CEA in-house TrioCFD code, a Verification and Validation study is proposed. Several LES of triple parallel jets are conducted with various grid sizes and SGS models. Following the idea of Celik et al. (2009), we look for the effective SGS kinetic energy under the form $k_{sgs}$ = $a\Delta ^p + b\Delta ^q$ , where $\Delta$ is the grid size, the order of the numerical scheme and the order of the subgrid-scale model. In a first part, no SGS model is set and two different calculations allow to determine the values of the parameters in the above model. Then, a SGS model is added and its order of convergence is calculated. Thus, one can assess the quality of various SGS models, such as Smagorinsky and WALE. In the last part, a Validation of the results is proposed by comparing computed velocity profiles to experiment. The effects of grid resolution, SGS model and boundary conditions are discussed.
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Submitted on : Friday, December 13, 2019 - 2:44:40 PM
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• HAL Id : cea-02339121, version 1

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P.-E. Angeli. Verification and validation in LES of triple parallel jet flow for a thermal striping investigation. CFD4NRS-7 OECD-NEA and IAEA Workshop Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation, Sep 2018, Shanghai, China. ⟨cea-02339121⟩

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