Cavitation and Size Scale Effects for Orifices

Cavitation data are presented for circular sharp-edged orifices which identify incipient, critical, moderate, heavy, and choking cavitation. The experimental program included pipe sizes from 1 to 23.5 in. (25 to 597 mm), pressures from 20 to 200 psi (140 to 1,400 kn/m²), and orifice size ratios from β = 0.332 to 0.884. Incipient and critical cavitation are affected by pipe size but are independent of pressure and velocity. Choking cavitation is independent of pressure, velocity, and size. An accelerometer was used to evaluate incipient and critical limits. Moderate and heavy cavitation regions were selected by aural observations. Choking flow was identified as the flow condition where the discharge coefficient began to rapidly decrease.