• Elliptical stirred vessels significantly improve mixing performance in unbaffled stirred tanks, reducing mixing time to 45.3% of that in circular tanks at an aspect ratio of 2.00.
• Increasing aspect ratio strengthens secondary flow and enlarges the vortex core region, enhancing fluid circulation and mixing.
• Axial velocity is more sensitive to aspect ratio changes than circumferential or radial velocity, indicating improved axial mixing.
• Elliptical geometry alters turbulent kinetic energy transfer, offering a novel approach to optimize mixing without baffles.