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Simulating Cavitation and Hydraulic Flip Inside Hydroentangling Nozzles

机译：模拟水力缠结喷嘴内的气蚀和水力翻转

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摘要

Hydroentangling owes its success to the peculiar properties of coherent water jets. For hydroentangling to be feasible at higher pressures, it is extremely important that water jets maintain their collimation for an appreciable distance downstream of the nozzle. However, water-jet breakup accelerates at high pressures. Recent studies have shown that cavitation severely affects the integrity of high-pressure water jets. Investigating cavita-tion experimentally is not trivial. Computational fluid dynamics simulations offer appropriate tools as a first step. This paper discusses the results of an unsteady-state simulation, which shows the inception and time-evolution of a cavitation cloud inside a hydroentangling nozzle. Under certain conditions, the cavity cloud extends to the nozzle outlet, resulting in the so-called hydraulic flip. Once hydraulic flip occurs, cavitation suddenly vanishes because the downstream air moves upward into the nozzle and fills the cavity. This air envelops the water flow inside the nozzle, which results in the depletion of cavitation-induced instabilities from the jet surface and elongates the jet breakup length. Moreover, our simulations reveal the approximate time scales of cavity growth through the nozzle. This information is highly relevant for experimental visualization of nozzle cavitation. The discharge and velocity coefficient obtained from the simulation are in a good agreement with published experimental data.
机译：水力缠结的成功归因于相干水射流的独特特性。为了使水力缠结在较高压力下可行，将水射流在喷嘴下游一定距离内保持准直非常重要。然而，在高压下水射流破裂加速。最近的研究表明，空化严重影响高压水射流的完整性。通过实验研究空化并非易事。作为第一步，计算流体动力学模拟提供适当的工具。本文讨论了非稳态模拟的结果，该结果显示了水力缠结喷嘴内空化云的发生和时间演化。在某些条件下，型腔云会延伸到喷嘴出口，从而导致所谓的液压翻转。一旦发生液压翻转，由于下游空气向上移动进入喷嘴并充满腔体，因此空化突然消失。这种空气包围喷嘴内的水流，导致空化引起的不稳定性从喷射表面消失，并延长了喷射破裂的长度。此外，我们的仿真揭示了通过喷嘴的腔体生长的大致时间尺度。该信息与喷嘴气蚀的实验可视化高度相关。通过模拟获得的流量和速度系数与已发布的实验数据非常吻合。

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  • 来源
    《Textile Research Journal》 |2004年第4期|p.359-364|共6页
  • 作者

    H. VAHEDI TAFRESHI; B. POURDEYHIMI;

  • 作者单位

    Nonwovens Cooperative Research Center, North Carolina State University, Raleigh, North Carolina U.S.A.;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 纺织工业、染整工业;
  • 关键词

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