Numerical Instability Study of Supercritical Water Flowing Upward in Two Heated Parallel Channels

Abstract

A three dimensional numerical investigation of supercritical water flowing upward in two heated parallel channels was developed using a RANS model in the Computational Fluid Dynamics (CFD) code ANSYS CFX. The standard k- turbulence model with scalable wall functions was adopted throughout this numerical study.The effects of spatial and temporal grid sizes on flow instability were studied first. Then oscillatory instabilities of nine experimental cases were predicted using the CFX code.For comparison purposes, Chatoorgoon"s 1-D non-linear SPORTS code was also used to determine the instability boundary. These new numerical results were compared with the experimental data and previous numerical results by other investigators.Additionally, the effects of changing the outlet plenum volume, the turbulent Prandtl number, the turbulence inlet conditions, the outlet K factor, the maximum iterations per time step in the transient analysis and the order of the transient scheme on the instability thresholds were examined.ii ACKNOWLEDGEMENTS