不同间距下过冷水滴连续撞击超疏水表面的数值研究

Numerical study of supercooled water droplets continuously impacting a superhydrophobic surface with different spacings

  • 摘要: 过冷水滴撞击飞机表面后形成的积冰严重威胁着飞行安全,积冰通常是由多个液滴共同作用形成的,明晰多过冷水滴间的相互作用对撞击-结冰过程的影响具有重要意义。本文基于流体体积法,结合凝固/融化模型,数值模拟了双过冷水滴连续撞击冷超疏水表面的动力学行为,研究了液滴间距对双液滴动态行为和传热特性的影响。结果表明:随着液滴间距的增加,双液滴依次出现了“内部铺展”,“表面铺展”和“包裹式铺展”三种混合模式,最大铺展系数由不变过渡到增大,双液滴的聚集行为逐渐加剧,液滴与冷壁面的传热效果随之增强,其中,液滴与冷表面的接触面积是影响传热的首要因素;此外,双液滴相互作用过程中液滴内部形成的旋涡会阻碍液滴的水平铺展,从而避免铺展面积的增大。

     

    Abstract: Supercooled water droplets impact the cold surface of an aircraft and form ice accumulations, which pose a threat to flight safety. Therefore, it is necessary to understand the dynamic behavior and phase transition process of these droplets. In this study, the dynamic process of double supercooled water droplets continuously impinging on a cold superhydrophobic surface (SHS) is numerically simulated using the Volume of Fluid (VOF) method in conjunction with the Solidification/Melting model. The study investigates the influences of droplet spacing and the Weber number (We) on droplet spreading and heat transfer characteristics. We observed three distinct mixing modes when double droplets impact at low Weber numbers: 'internal spreading', 'surface spreading', and 'shower spreading'. As the spacing between droplets increases, these modes appear in sequence. The maximum spreading factor transitions from a constant value to an increasing one, and the aggregation behavior of the double droplets intensifies. In the 'internal spreading' mixing mode, the vortices formed inside the double droplets impede the horizontal spreading, thus preventing an increase in the spreading area. Moreover, as the droplet spacing increases, the heat transfer between the droplets and the cold surface is enhanced. The contact area of the droplets with the cold surface is a decisive factor in heat transfer, outweighing the influence of the local heat transfer coefficient. This study enhances our understanding of the dynamics and heat transfer of double supercooled water droplets continuously impinging on a cold superhydrophobic surface (SHS) and contributes to the development of anti-icing and de-icing technologies.

     

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