Large Eddy Simulation of sodium flow in a tee junction. Comparison of temperature fluctuations with experiments

In the frame of the thermal stripping study, this paper presents two numerical approaches. Both the TRIO-VF and STAR-CD codes are used to compute the characteristics of temperature fluctuations occurring in a tee mixing hot and cold sodium pipe flows. TRIO-VF uses a Large Eddy Simulation applied on a structured mesh model, fluctuating boundary conditions are prescribed by performed a previous calculation of a straight pipe. STAR-CD applies a pseudo Direct Numerical Simulation on an unstructured mesh model describing closely the tee junction. The evaluations of the two calculations are performed by comparing with available experimental measurements performed on a sodium test loop. The main result is the obtaining of a good agreement of the mean temperature profiles if the geometry is strictly respected (STAR-CD approach) and a LES model is not obligatory required to compute fluctuating flows in an industrial way. A good prediction of the amplitude of the thermal fluctuations and a satisfactory assessed range of frequencies is obtained in both calculations. Furthermore, the computation at the same time of the conduction within the wall allows to get the value of attenuation of the fluctuations and the instant thermal fields obtained in the metal at every time permits mechanical calculations of the damages due to the thermal stripping. (author)