Drag reduction induced by asymmetric grooves in turbulent Taylor-Couette flow at large radius ratio in high-speed canned motor pumps

Turbulent Taylor-Couette flow is widely present in high-speed rotating machinery, especially in equipment with rotor-stator structures. This study focuses on the drag reduction optimization of asymmetric triangular groove structures in turbulent Taylor-Couette flow within the clearance of a canned motor pump under high rotational speed and a large radius ratio ( η = 0.934). Using numerical simulation methods, the effects of groove height ( H = 0.025, 0.05, and 0.075 mm) and their placement on the inner and outer walls on flow resistance were systematically analyzed, covering Taylor numbers ( Ta ) ranging from 1.06×10 8 to 4.72×10 9 . The study shows that the drag reduction performance of the grooves significantly depends on the Taylor number, groove height, and location: at medium and lower Taylor numbers, grooves on the inner wall provide superior drag reduction (with a maximum drag reduction rate of 12.29%), and the effect improves with increasing groove height. In contrast, at high Taylor numbers, grooves on the outer wall exhibit better drag reduction performance, achieving a drag reduction rate of 6.16%. Flow field analysis shows that the grooves induce near-wall vortices, stabilize Taylor vortices, reduce turbulence and shear stress, thereby suppressing peak turbulent kinetic energy by up to 37.5% (inner wall) and 22.8% (outer wall).