主管部门: 中国航天科技集团有限公司
主办单位: 中国航天空气动力技术研究院
中国宇航学会
中国宇航出版有限责任公司

气泡碰壁受力模型和反弹规律

Force Balance Model and Bubble Rebound Law for Bubble-Wall Collision

  • 摘要:Mo=10-8~10-12Re=5~750范围内的上升气泡与壁面垂直碰撞问题进行了理论求解,研究了不同控制参数下气泡碰壁反弹的规律.气泡上升和碰撞过程的运动方程考虑了浮力、液体阻力、附加质量力和与壁面碰撞时引起的薄膜诱导力.气泡碰壁过程气泡界面与壁面形成的液膜厚度变化规律由Stokes-Reynolds方程计算得到.膜内气泡变形引起的流体压强采用Young-Laplace方程求解.结果表明,基于SRYL方程的薄膜诱导力模型可以很好地预测不同Reynolds数下气泡0到多次的反弹轨迹,计算结果与实验结果吻合良好.气泡在碰壁反弹过程中会形成丰富的薄膜形状,如酒窝状变形,丘疹状变形和涟漪状变形.气泡界面变形会引起膜内压强的变化,压强的分布规律与气泡界面形状有着重要的关系.气泡在与壁面碰撞的过程中,薄膜诱导力会起主导作用,且随着Reynolds数的增加薄膜诱导力最大量级增大.气泡碰撞壁面时,反弹次数与Reynolds数有着直接的联系,不同Morton数下的气泡均在相同Reynolds数附近发生气泡反弹次数的变化.

     

    Abstract: The vertical collision of rising bubbles in liquids against rigid wall in the range of Morton numbers Mo=10-8~10-12 and Reynolds numbers Re=5~750 were analyzed theoretically and the bubble rebound law was studied. The equations of motion for bubble rising and colliding with wall take into account buoyancy force, liquid resistance, added mass force and film-induced force. The variation of liquid film thickness between bubble interface and wall was calculated by Stokes-Reynolds equation. The fluid pressure caused by bubble deformation in membrane was solved by Young-Laplace equation. The results show that the film-induced force model based on SRYL equation can well predict the rebound trajectory of the bubble. The bubble can rebound from 0 to many times with increasing Reynolds number, and the calculated results are in good agreement with the experimental results. During bubble collision and rebound from the wall, bubble interface formed abundant film shapes, such as dimple, pimple and wimple. Deformation of the bubble interface caused the change of pressure in the film. The distribution of pressure is closely related to the shape of bubble interface. The film-induced force plays a dominant role on the bubble motion when bubble interacts with rigid wall. The maximum induced force increases with the increase of Reynolds number. The number of rebound times of air bubble is directly related to the Reynolds number. The critical Reynolds number for the transition of bubble rebound times is almost the same at different Morton numbers.

     

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