Interfacial oscillation of liquid jets discharging from non-circular orifices

This work presents an experimental study on the oscillation behavior of liquid jets discharging from elliptical, triangular, and square shaped non-circular orifices. The measurements of wavelength and amplitude of jet oscillation are extracted from digital images of the liquid jets captured via still photography technique at different flow conditions using three different liquids (pure water, water-glycerol mixture, and Jet A-1 fuel). The measured wavelength of jet oscillation (λ), irrespective of the shape geometry of the tested non-circular orifices, increases linearly with increase in liquid jet velocity (Uo) and scales with the liquid jet Weber number (We) as λ/Deq ∝ We0.5. The experimental measurements of λ recorded at different flow conditions exhibit good agreement with the theoretical predictions obtained using the mathematical model proposed by Rayleigh (1879) for liquid jet undulating in its cross section. For a given Uo, the liquid jet of Jet A-1 displays higher value of λ and undergoes a larger increase in λ along the axis of the jet compared to the jets of other two liquids. Further the trends on the variation of maximum and minimum amplitudes of the first wave segment of liquid jets discharging from the elliptical and square orifices with Uo are discussed.