Numerical simulation of evolution pattern of vortices in Taylor-Couette flow with three-lobe multiwedge clearance

Gas foil bearings have been utilized in high-speed rotational machinery due to their superiority of load capacity and stability, which are closely associated with the shearing flow induced by variable sections in multiwedge clearance. This study focuses on the evolution pattern of vortices in Taylor-Couette flow with three-lobe multiwedge clearance using large-eddy simulation. As the Taylor number (T-a) increases, the shearing flow transitions from separation flow to Taylor vortex flow, followed by secondary transitions leading to wavy vortex flow. Separation vortices occur around the joint between two lobes, significantly delaying the first transition. Subsequently, Taylor vortices emerge and interact with the separation vortices, resulting in a complex evolution pattern of vortex series with increasing T-a. The presence of separation vortices promotes the formation of angular periodicity in Taylor vortices, accelerating the occurrence of angular periodicity stall and enhancing energy exchange between adjacent Taylor vortices. Taylor vortices are prone to breaking and merging. Additionally, Taylor vortices disrupt the shear layer of separation vortices between the stall region and the mid-radius separation region, leading to the migration of the shear layer and the singularity toward the mid-radius. Consequently, separation vortices move toward the mid-radius and transform from a one main vortex structure to two main vortex structures. Furthermore, spectral analysis of turbulent kinetic energy (TKE) reveals an inverse energy cascade characteristic with a slope of -7/3 at high frequencies, attributed to the TKE transmission between Taylor vortices and separation vortices. Both types of vortices exhibit intermittent and periodic behavior.