放射状自由液膜流れの乱流遷移によるせん孔現象とせん孔の促進および抑制要因(流体工学,流体機械)

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Perforations caused by a laminar-turbulent transition of a radial liquid sheet are described. A liquid film produced by an impingement of liquid to a disk center spreads out radially on the disk and forms a radial liquid sheet outside the disk edge. The radial liquid sheet is unstable because of an internal velocity profile with an inflexion point. The instability causes a laminar-turbulent transition just outside the disk edge and the transition leads to strong turbulence. Flow patterns completely depend on the frequency of perforations produced by the strong turbulence. The countless perforations lead to atomization of the liquid sheet and no perforation results in a smooth liquid sheet. The perforation frequency relies on the configurations of aggregations produced by fine waves after the transition. The wavy short aggregations induce the countless perforations and atomization immediately after the transition. The perforation frequency also relies on liquid properties and temperature of ambient air flow. Chemical properties of the liquid sustaining a very thin liquid sheet of a bubble suppress the perforation and hot ambient air flow promotes the perforation.
2007-05-25