89 research outputs found

    Bubble Entrainment, Spray and Splashing at Hydraulic Jumps

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    The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong energy dissipation and air entrainment, waves and spray. New two-phase flow measurements were performed in the developing flow region using a large-size facility operating at large Reynolds numbers. The experimental results demonstrated the complexity of the flow with a developing mixing layer in which entrained bubbles are advected in a high shear stress flow. The relationship between bubble count rates and void fractions was non-unique in the shear zone, supporting earlier observations of some form of double diffusion process between momentum and air bubbles. In the upper region, the flow consisted primarily of water drops and packets surrounded by air. Visually significant pray and splashing were significant above the jump roller. The present study is the first comprehensive study detailing the two-phase flow properties of both the bubbly and spray regions of hydraulic jumps, a first step towards understanding the interactions between bubble entrainment and droplet ejection processes

    Injection Characteristics on the Surface of a Coaxial Jet

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    Coarsening of intermetallic or compound precipitates in binary systems

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    A special form of equation r̄ -r̄ = 8x (∞)DσV /9RT 1-x (∞)/(x (∞)-x (∞)) t or equation r̄ -r̄ = 8DσV /9 G (x (∞)-x (∞)) t was presented for the coarsening of stoichiometric compound precipitates in a binary system. The modification is based on the facts that the Gibbs-Thomson equation for a compound precipitate and the mass balance equation for the growth of a compound precipitate are somewhat different from those for a solid-solution precipitates
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