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Capillary bridge stability and dynamics: Active electrostatic stress control and acoustic radiation pressure.

机译：毛细管桥的稳定性和动力学：主动的静电应力控制和声辐射压力。

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摘要

In low gravity, the stability of liquid bridges and other systems having free surfaces is affected by the ambient vibration of the spacecraft. Such vibrations are expected to excite capillary modes. The lowest unstable mode of cylindrical liquid bridges, the (2,0) mode, is particularly sensitive to the vibration when the ratio of the bridge length to the diameter approaches pi. In this work, a Plateau tank has been used to simulate the weightless condition. An optical system has been used to detect the (2,0) mode oscillation amplitude and generate an error signal which is determined by the oscillation amplitude. This error signal is used by the feedback system to produce proper voltages on the electrodes which are concentric with the electrically conducting, grounded bridge. A mode-coupled electrostatic stress is thus generated on the surface of the bridge. The feedback system is designed such that the modal force applied by the Maxwell stress can be proportional to the modal amplitude or modal velocity, which is the derivative of the modal amplitude. Experiments done in the Plateau tank demonstrate that the damping of the capillary oscillation can be enhanced by using the electrostatic stress in proportion to the modal velocity. On the other hand, using the electrostatic stress in proportion to the modal amplitude can raise the natural frequency of the bridge oscillation. If a spacecraft vibration frequency is close to a capillary mode frequency, the amplitude gain can be used to shift the mode frequency away from that of the spacecraft and simultaneously add some artificial damping to further reduce the effect of g-jitter.; It is found that the decay of a bridge (2,0) mode oscillation is well modeled by a Duffing equation with a small cubic soft-spring term. The nonlinearity of the bridge (3,0) mode is also studied. The experiments reveal the hysteresis of (3,0) mode bridge oscillations, and this behavior is a property of the soft nonlinearity of the bridge.; Relevant to acoustical bridge stabilization, the theoretical radiation force on a compressible cylinder in an acoustic standing wave is also investigated.
机译：在低重力下，液桥和其他具有自由表面的系统的稳定性会受到航天器周围环境振动的影响。预期这种振动会激发毛细管模式。当桥的长度与直径的比率接近pi时，圆柱形液体桥的最低不稳定模式（2,0）对振动特别敏感。在这项工作中，使用了高原坦克来模拟失重状态。光学系统已被用于检测（2,0）模式振荡幅度并生成由振荡幅度确定的误差信号。反馈系统使用该误差信号在与导电接地电桥同心的电极上产生适当的电压。因此，在桥的表面上产生模式耦合的静电应力。设计反馈系统，以使麦克斯韦应力所施加的模态力与模态振幅或模态速度成比例，这是模态振幅的导数。在高原储罐中进行的实验表明，通过使用与模态速度成比例的静电应力，可以增强毛细管振荡的阻尼。另一方面，使用与模态振幅成比例的静电应力可以提高电桥振荡的固有频率。如果航天器的振动频率接近毛细管模式频率，则可以使用幅度增益来使模式频率偏离航天器的频率，并同时增加一些人工阻尼，以进一步减小g抖动的影响。发现通过具有小的三次软弹簧项的Duffing方程可以很好地建模桥（2,0）模式振荡的衰减。还研究了桥（3,0）模式的非线性。实验揭示了（3,0）模式电桥振荡的磁滞，此行为是电桥软非线性的特性。与声桥稳定有关，还研究了声驻波中可压缩圆柱体上的理论辐射力。

著录项

  • 作者

    Wei, Wei.;

  • 作者单位

    Washington State University.;

  • 授予单位 Washington State University.;
  • 学科 Physics Fluid and Plasma.; Physics Acoustics.; Physics Radiation.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 152 p.
  • 总页数 152
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 等离子体物理学;声学;原子核物理学、高能物理学;
  • 关键词

  • 入库时间 2022-08-17 11:42:40

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