Dynamic Behavior Of A Bubble Rising Near A Vertical Wire-mesh

Gas-liquid two-phase flow is widely used in engineering fields such as fuel cell,aero engine,chemical reactor,bubble reactor,mineral flotation,and other multiphase mixed transmission and mass and heat transfer.Wire-mesh has a good application prospect in the design of multi-phase flow systems with efficient heat and mass transfer performance.The research of bubble rising near a vertical mesh is helpful for the further understanding of the bubble-wall mechanism and also can provide theoretical support for the heat and mass transfer near wire-meshes.In this paper,the dynamic behavior of a bubble rising near a vertical wire-mesh at high Reynolds number is experimentally investigated.The dynamic parameters,shape oscillation,force model,and energy components are discussed.The high-speed shadowgraphy system was used to record the effects of different porosities on the mesh(57%,41.9%,37.9%)and initial distance s~* on the dynamic behavior of a bubble rising near the meshes.And then compared to the cases of a bubble rising near impermeable walls.The results show that the near-mesh bubble always travels within a spiral trajectory at different s~*,similar to the free-spiraling bubble.Due to the weaker blockage-effects of the high porosity of meshes,the bubble has a larger inertial effect,so that bubble-mesh collisions only occur at the minimum s~*.The high porosity of the mesh makes it a slip boundary condition with a non-zero normal velocity.Compared with the impermeable wall,a mesh is an insignificant enough interference on the bubble wake,which suppressing the symmetric vortex shedding and then the transition of paths from spiraling into zigzagging.However,meshes still inevitably have a certain wall effect on bubbles.The interference of meshes can cause the transition and fluctuation in the characteristic frequencies of the lateral migration,velocity,and shape oscillation.In terms of energy,horizontal momentum components are transferred to each other to maintain bubbles rising in spiral motions.The lower energy dissipation further explains why bubbles do not collide with the Mesh-S.This study will help predict or modify the distribution of gas void fractions near a vertical wire-mesh,thereby improving rates of mass and heat transfer in related engineered systems.