Characteristics of flow through small sharp-edged cylindrical orifices

Abstract The discharge coefficients for flow through small sharp-edged cylindrical orifices of diameters between 0.3 and 2 mm and aspect ratios between 1 and 50 are evaluated. The characteristics of flow in the separated, attached and cavitated flow regions are determined. It is shown that while the discharge coefficient scales with the Reynolds number and aspect ratio in the attached flow regions, the diameter influences the discharge coefficient in the separated flow region. 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.