Baffles are vertical plates projecting from the vessel wall (typically 4 baffles, width = D_tank/10–12) that break the tangential swirling flow caused by impeller rotation. Without baffles, liquid rotates as a solid body (vortex), producing poor mixing and reduced gas dispersion. Baffles convert rotational energy into radial and axial flow, dramatically improving mixing homogeneity and oxygen transfer efficiency.