受限空间内旋流回流区特性

Recirculation Zones of Swirling Flow in Confined Space

为了研究受限空间内旋流回流区的三维结构特性,采用realizable k-ε模型模拟了旋流数等于0.884时,不同受限空间内的旋流流场.受限率是影响回流区形态的重要因素,受限率大于6时,中心回流区与下游回流区是两个独立的区域,有两对涡结构;受限率在3~6之间时,中心回流区与下游回流区合并到一起,存在两对独立的涡结构;受限率小于3时,流场截面内形成一个气泡状的中心回流区,有唯一的一对涡结构.受限率在3附近时,存在一个过渡状态,回流区的形成过程与其他工况明显不同,先后出现了多螺旋、单螺旋、双螺旋的涡核进动形式,其中单螺旋和双螺旋的涡核进动方向与多螺旋涡核进动方向相反.

In order to study the three-dimensional structure of recirculation zones of swirling flow in confined space,realizable k-εmodel was used to simulate the swirling flow field in different confined space with the swirl number of 0.884.The confinement ratio is an important factor affecting the shape of recirculation zone.When the confinement ratio goes above 6,the central recirculation zone and the downstream recirculation zone are two independent zones with two pairs of vortices.When the confinement ratio is between 3~6,the central recirculation zone and the downstream recirculation zone are merged together,and there are two pairs of independent vortices.When the confinement ratio is less than 3,a bubble-shaped central recirculation zone is formed in the flow field with a unique pair of vortices.When the confinement ratio is around 3,there will be a transition state,in which the formation process of the recirculation zone is obviously different from other conditions.In this state,vortex core structures of multi helix,single helix and double helix appear successively.The spiral direction of single and double helix vortex procession is opposite to that of the multi helix.