Abstract
Quantifying accidental opaque discharges is a challenging task, since probing beyond their visible interfaces may be difficult or impossible. In this case, we show that the visible interface features near the jet exit can be used to gauge the flow. This work examines the interface in the near-field features of submerged homogeneous and immiscible turbulent jets. Experiments were carried out with water jets and immiscible silicone oil jets of two viscosities in a water tank. The jet Reynolds numbers are in the range of $Re\sim 4500{-}50\,000$ for homogeneous water jets and $Re\sim 3500{-}27\,000$ for silicone oil jets in water. The jet fluids are made visible by doping with fluorescent dye and excitation with directional illumination. The jet interfaces are continuous and convoluted for water jets, while convoluted and discontinuous with droplets and ligaments for oil jets. Direct flow visualization, schlieren photography, shadowgraph photography and particle image velocimetry are employed as appropriate. Interface length scales are characterized using various image processing techniques. Droplet sizes are quantified using Hough transformation. Interface length scales decrease with Reynolds number and increase gradually with distance from the exit plane for a given Reynolds number. These scales are isotropic for the homogeneous water jets and exhibit a streamwise-to-cross-stream ratio of approximately 1.3 for the oil jets. Interfacial tension, hence the Weber number, determines the average droplet size in the immiscible jets.
Highlights
Yule (1978) presents measurements in air and visualization in water in the near field of well-engineered jets where the flow is dominated by toroidal vortices
Shaffer et al (2015) conducted a series of experiments exploring techniques to extract flow rates from video images. They show that a routine application of particle image velocimetry (PIV) software to a video of the Deepwater Horizon oil leak jet, a frame of which is shown in figure 1(a), yields velocities that are 10 %–50 % lower than manual measurements of velocities from the advection of the interface features
Within the near field that we investigated, the Morton length scale (Morton 1959; Turner 2012) was sufficiently large to neglect buoyancy effects on the flows for the oil runs listed in table 2
Summary
Yule (1978) presents measurements in air and visualization in water in the near field of well-engineered jets where the flow is dominated by toroidal vortices. Bogusławski & Popiel (1979) present hot-wire measurements in the extended near field (x/D < 12) of a jet discharging from a fully developed turbulent pipe flow. Dimotakis, Miake-Lye & Papantoniou (1983) present laser-induced fluorescence (LIF) measurements in the far field of turbulent water jets over the Reynolds number range of 500 to 10 000 and conclude that large-scale structures, both circular or helical, are persistent in the flow field. Savas (2012) carried out a series of dye flow visualization experiments in water to study the visible flow features in the near field of turbulent jets at Reynolds numbers of (0.3–2.2) × 105. The paper ends with concluding remarks and our parting thoughts
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