Transient Behavior of Boundary Layer Flows in a Prototype Rotor-Stator Cavity During an Instantaneous Spinning-Up Process

Abstract

Abstract The transient dynamics of boundary layer flows in a prototype rotor-stator cavity during spinning-up process is investigated using Large Eddy Simulation (LES). Various stages of temporal evolution are discerned by examining the torque coefficient on both the stator and rotor plates. The rotor boundary layer temporal evolution can be divided into three stages, involving an instantaneous spinning-up process, a subsequent torque coefficient decrease influenced by viscous forces, and the final stabilization. Simultaneously, the stator boundary layer undergoes a continuous velocity increases driven by initial cavity recirculation and axial momentum transfer before reaching final stabilized stage. Vortical structures induced by type I crossflow instability play a pivotal role in the transient evolution of the studied system. In the rotor boundary layer, these structures form rapidly, undergo elongation and stretching in the second stage, facilitating axial momentum transfer. However, in the final stage, these vortical structures vanish, coinciding with the laminar nature of the rotor boundary layer. In contrast, the stator boundary layer exhibits a different behavior. Vortical structures in this layer gradually emerge and persist until the flow reaches its final stabilization, in accordance with the turbulent nature of the stator boundary layer. This comprehensive investigation enhances the understanding of the intricate dynamics within rotor-stator cavities.