Abstract
The dynamic process of circular water jets plunging into a quiescent pool was analyzed in this study based on the RNG k∼ε turbulence model and VOF method. The effects of jet velocity and inclination angles relative to horizontal on the cavity shapes and sizes were analyzed. The simulation successfully captured the formation, development, pinch-off, and disintegration phenomena of cavities. The shape of the cavity is mainly affected by the impact angle, while the impact velocity mainly affects the size of the cavity. The cavity pinch-off initially appears at a certain point in any direction for vertical jets, while the cavity in the opposite direction of flow pinch-off appears before the cavity in the direction of flow for inclined jets. Before cavity pinch-off, the maximum radial and axial sizes of the cavity generally increase with the impact velocity and the time after impingement. The axial penetration velocity of the cavity tip is approximately half of the impact velocity, which is consistent with previous research. Finally, based on the statistics of the cavity sizes, empirical formulas for predicting the maximum radial and axial sizes of the cavity were established.
Highlights
E dynamic process of circular water jets plunging into a quiescent pool was analyzed in this study based on the RNG k∼ε turbulence model and VOF method. e effects of jet velocity and inclination angles relative to horizontal on the cavity shapes and sizes were analyzed. e simulation successfully captured the formation, development, pinch-off, and disintegration phenomena of cavities. e shape of the cavity is mainly affected by the impact angle, while the impact velocity mainly affects the size of the cavity. e cavity pinch-off initially appears at a certain point in any direction for vertical jets, while the cavity in the opposite direction of flow pinch-off appears before the cavity in the direction of flow for inclined jets
Zhu et al [5] described the cavity characteristics of a vertical jet based on experimental pictures and theoretical analysis. eir results showed that the maximum radial size of the cavity changed with Fr(01/4) (Fr0 nozzle), and the is the Froude number at the exit of the axial size changed with Fr(01/3)
We mainly focus on the impact velocity, angle, and time of the water jet
Summary
E effects of jet velocity and inclination angles relative to horizontal on the cavity shapes and sizes were analyzed. Before cavity pinch-off, the maximum radial and axial sizes of the cavity generally increase with the impact velocity and the time after impingement. 1. Introduction e phenomenon of air entrainment often occurs when a water jet from air plunges into a pool. Soh et al [6] believed that the maximum axial size of the cavity for vertical jets varied with Fr(01/3). Mainly focused on the air entrainment characteristics after cavity disintegration, indicating that the maximum air concentration decreased exponentially with the axial distance from the impact point, and obtained an empirical. Dis the diameter of a nozzle; Frj is the Froude numbers, Frj (V2j /g D) for circular jets, Frj (V2j /gTj) for plane jets, Vj is the impact velocity, Tj and Wj are the jet thickness and width at impact point for plane jets, θj is the jet inclined angle relative to horizontal at the impact point
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