CFD-based analysis of dynamic coefficients in labyrinth seals with teeth on stator: comparison with bulk-flow models

Maintaining effective sealing in turbomachinery is critical to operational stability and efficiency. Labyrinth seals, widely used for their favorable leakage control, can introduce destabilizing forces that affect rotor dynamics. This study investigates the calculation of dynamic coefficients in straight labyrinth seals with teeth on the stator (TOS) using a three-dimensional Computational Fluid Dynamics (CFD) approach based on the Precessional Rotor Method. The CFD results are compared with those from established bulk-flow models—LABY3 and XLLaby1CV. Significant discrepancies in dynamic coefficients and leakage predictions are observed, particularly in the sign and magnitude of the direct stiffness. Auxiliary static simulations are used to analyze the pressure fields responsible for these differences. The CFD model captures pressure distribution behavior similar to that observed in prior work, where kinetic energy (KE) carryover factors in bulk-flow models were adjusted to match experimental trends. These findings highlight the importance of accurate pressure modeling near the first seal teeth and suggest potential improvements to bulk-flow leakage models. The main contribution of the present work is to provide a detailed analysis for understanding the discrepancies between CFD and bulk-flow predictions, and to assess the sensitivity of dynamic coefficients to domain extent in CFD simulations.