Cavitation bucket

The cavitation bucket is the bucket-shaped region on a plot of cavitation number sigma against angle of attack (or lift coefficient) inside which a blade section runs free of cavitation. Its floor is the minimum sigma a section tolerates at its design incidence; its two walls mark the angles where face (pressure-side) cavitation and back (suction-side) cavitation set in as incidence swings negative or positive. A wide, deep bucket means the section keeps a cavitation-free margin across the angle range the spatially varying wake imposes each revolution. Section camber and thickness shape the bucket: more camber shifts it toward higher design lift, more leading-edge radius widens it against off-design incidence.