Abstract The flow field developing inside the stator-rotor disc cavities of gas turbines is characterized by highly complex and unsteady behavior driven by strong vortical structures and transient interactions. These features pose significant challenges for accurate prediction using standard Computational Fluid Dynamics (CFD) models. In particular, the inherent unsteadiness of the flow field has a considerable impact on the sealing performance of the rim, especially when predicted by steady Reynolds-Averaged Navier-Stokes (RANS) methods, which tend to overestimate the sealing effectiveness. In this study, numerical simulations were conducted using RANS, unsteady RANS (URANS), and Large Eddy Simulation (LES) approaches to analyze the rim seal flow. The results were compared with experimental data from the University of Florence's test rig. The RANS, URANS, and LES simulations showed satisfactory agreement in terms of steady-state pressure coefficients and velocity fields. However, the Reynolds-averaged models failed to capture turbulent fluctuations between the main and secondary flows, while LES accurately resolved vortex development and unsteady interactions, matching experiments more closely. These fluctuations are now recognized as a key factor driving mainstream flow ingestion into the cavity. Resolving them is crucial for understanding the unsteady interaction between the main and secondary flows. Although LES requires high computational cost and long transient phases to achieve periodic convergence, it proves to be a powerful tool for predicting these complex flow dynamics. The study demonstrates LES's potential for improving rim seal flow predictions compared to traditional RANS approaches.
Geronimo et al. (Mon,) studied this question.