Effect of the Accuracy Order of the Discretization Scheme on the Prediction Performance for the Turbulent Flow Structure Inside Fuel Assembly: Sensitivity Study

Abstract

Spatial discretization errors result from both the numerical order of accuracy of the discretization scheme, and from grid spacing. It is well known that second, or higher, order discretization schemes are potentially able to produce high-quality solutions. In addition, when either the flow is not aligned with the grid, or is complex, it is recommended that the first order discretization scheme not be used for the convection term, if possible. However, the higher-order scheme can also result in convergence difficulties and instabilities at certain flow conditions. In this study, to examine the effect of the numerical order of accuracy of the discretization scheme on the prediction accuracy for the turbulent flow structure inside fuel assembly with the split-type mixing vanes, simulations were conducted with the commercial CFD (Computational Fluid Dynamics) software, ANSYS CFX R.14. Two different types of the discretization scheme for the convection-terms-of-momentum and -turbulence equations, i.e. 1st order upwind scheme and a high resolution scheme, were used. The predicted results were compared with the measured data from MATiS-H (Measurement and Analysis of Turbulent Mixing in Subchannles-Horizontal) facility, installed in the KAERI (Korea Atomic Energy Research Institute).