Dynamic behavior of a deformable bubble rising near a vertical wire-mesh in the quiescent water
Dynamic behavior of a deformable bubble rising near a vertical wire-mesh in the quiescent water
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静止水中垂直丝网附近上升的可变形气泡的动态行为
DOI：
10.1016/j.expthermflusci.2020.110235
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发表时间：
2021
影响因子：
3.2
通讯作者：
Bao Fubing
中科院分区：
文献类型：
--
作者：
Chen Yeyu;Tu Chengxu;Yang Qincan;Wang Yukun;Ye Yuhang;Chen Qiang;Jiang Renjie;Yang Meng;Bao Fubing
由于丝网在设计高效传热传质系统方面具有很大的应用潜力，本文利用高速阴影摄影装置研究了Re ~ 800的可变形气泡在不同孔隙率的丝网附近的静止自来水中的上升过程。我们重点研究了三种网格（Mesh-L、Mesh-M和Mesh-S）的边界条件和初始壁距 * 对气泡在网格存在下上升的动力学行为的影响。与自由上升气泡和近壁气泡的情况相比，讨论了气泡的动力学参数、形状振荡和能量分量。结果表明，在不同的初始壁面距离下，近网格气泡始终以三维螺旋轨迹运动，与相应的自由螺旋气泡相似。网格-气泡碰撞仅发生在网格-L和网格-M上，在最小的初始距离 *= 0.11处，这是由于它们在网格之前和之后作为液体通过它的较低的压降，并且对气泡产生较强的附加质量效应。与无滑移壁面相比，网格作为壁面法向速度为非零的滑移边界条件，对气泡尾迹的干扰较小，抑制了对称涡脱落，进而抑制了气泡路径由螺旋形向螺旋形的转变。网格的干涉会导致横向偏移、速度和对称形状振荡的特征频率发生跃迁和明显的波动。在能量方面，近网孔上升气泡的水平动量分量相互传递以维持螺旋运动。气泡-网格碰撞的不存在可以解释为什么仅由Mesh-S产生的能量耗散ED略有变化并维持在较低水平at *< 9.05，而由其他壁或网格引起的ED不能达到这个低水平直到 *> 4.58。本文的研究结果对预测或修正近网格含气率分布以及改善相关工程系统的传质、传热性能具有一定的指导意义。
Because wire-meshes have a great potential application for designing high-efficient heat and mass transfer systems, a deformable bubble of Re ~ 800 rising in still tap-water near a vertical mesh of different porosity is studied using a high-speed shadowgraphy apparatus including two mutually perpendicular projections. We focus on the effect of the boundary conditions with three types of meshes (Mesh-L, Mesh-M, and Mesh-S) and initial wall distances*on the dynamic behavior of the bubbles rising by the presence of the meshes. The dynamic parameters, shape oscillation, and energy components are discussed, compared to the cases of the free-rising bubbles and that near impermeable walls. Results show that the near-mesh bubble always travels within a three-dimensional spiral trajectory at different initial wall distances, similar to the corresponding free-spiraling bubble. The mesh-bubble collisions only happen on the Mesh-L and Mesh-M, at the smallest initial distances*= 0.11, due to their lower pressure drop before and after the mesh as a liquid through it and causing the stronger added mass effect on the bubbles. Compared to the no-slip wall, the mesh, as a slippery boundary condition of non-zero wall-normal velocity, has insignificant interference on the bubble wake, suppressing the symmetric vortex shedding and then the transition of the bubble path from spiraling into zigzagging. The interference of the mesh can lead to the transition and obvious fluctuation in the characteristic frequencies of the lateral migration, velocity, and symmetric shape-oscillation. In terms of energy, the horizontal momentum components of a near-mesh rising bubble are transferred to each other to maintain the spiral motion. The absence of bubble-mesh collisions may explain why just the energy dissipationEDgenerated by Mesh-S changes slightly and maintains at a lower level ats*< 9.05, whileEDcaused by other walls or meshes cannot achieve this low level untils*> 4.58. It is expected that our findings will be helpful to predict or modify the near-mesh gas void-fraction distribution and to improve mass, heat transfer in related engineered systems.
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影响因子：
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