Viscous and unsteady flow calculations of condensing steam in nozzles

The paper presents two-dimensional calculations for spontaneously nucleating flows of steam in converging–diverging nozzles. The Reynolds-averaged Navier–Stokes equations are solved for the two-phase mixture, using a Jameson-style finite volume method on an unstructured and adaptive triangular mesh. Results are first presented for steady, viscous flow, showing the influence of boundary layer growth on streamwise pressure distributions and droplet sizes. These results have implications for the interpretation of some of the experimental data used for validating the theories of nucleation and droplet growth. The numerical scheme has also been applied to compute unsteady flows in a variety of nozzle geometries, covering a range of inlet conditions in each case. Asymmetric oscillation modes, previously observed in moist air, have been predicted for one of the geometries, indicating for the first time that such oscillations are possible in pure steam.