A numerical stability study of supercritical water in a vertical pipe is performed using RANS models in ANSYS CFX vl4.5. The threshold of oscillatory instability is determined using the k-ε and the SST turbulence models, results are compared with 1-D non-linear code solutions, and a condition for approximating the oscillatory instability threshold is assessed. Results show good agreement on the instability boundary between the k- ε and the SST turbulence models, while a 1-D non-linear code with the Blasius friction factor formula under-predicts the mass flow rate at the oscillatory instability threshold obtained using the CFD code.
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