Reduced order modelling for a rotating cavity flow using proper orthogonal decomposition.

In this thesis, attention is focused on computational modelling of the type of rotating cavity flows commonly encountered in secondary air systems. The first part of the thesis is devoted to improving the predictive modelling capabilities for these flows. The LES solver used in the current work has been validated for the non-buoyancy dominated flow of a rotating cavity with radial inflow. The swirl ratio predicted by different sub-grid scale models tested is in good agreement with the measurements, although a slight overprediction is observed at lower radii. This has been demonstrated to be caused by an excessive numerical dissipation. Adopting a stable, less dissipative I-LES solution, the swirl ratio matches the data almost perfectly. In the next activity, the prediction from a Large-Eddy Simulation conducted for a rotating cavity with a radial inflow introduced from the shroud and heated on one wall have been compared with experimental data available from the literature, and with those obtained using two URANS eddy-viscosity models. The LES solution has shown a very good agreement especially in the outer part of the cavity, capturing buoyancy effects. The results of two URANS models are considerably worse than the LES. Since LES is currently limited for application in industry by the high computational demand, Reduced Order Methods (ROM) that use data from LES have been considered in order to construct a model which could result in a computationally efficient method for design purposes. The POD-Galerkin procedure has been validated for the relative simple turbulent shear flow of the plane Couette flow. Then, the low Mach number turbulent flow in a rotor-stator cavity has been modelled. Overall, it is possible to claim that the models studied reasonably well predict the turbulence phenomenon for the rotor-stator flow (LES statistics and experimental measurements have been used as a benchmark)