In this experimental study, discharge coefficients for flow through small sharp-edged cylindrical orifices of diameters between 1 and 0.0984 in and aspect ratios between 1 and 40 are measured. For the determination of the flow characteristics, three regions are considered; separated, attached and cavitated flow regime. The results show that while the discharge coefficient scales with the Reynolds number and aspect ratio in the attached flow regime, the diameter influences the discharge coefficient in the separated flow regime. The onset of cavitation in the orifice is also seen to be dependent on the diameter and aspect ratio. The hysteresis in the flow and the violent disintegration of the jet observed for an aspect ratio of about 5 are discussed.

sharp-edged orifices, discharge coefficient, attached flow, cavitated flow.