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DIRECT NUMERICAL SIMULATION OF HEAT TRANSFER MECHANISM IN SEPARATED FLOW

分流传热机理的直接数值模拟

基本信息

批准号：
12650190
负责人：
OTA Terukazu
金额：
$ 2.11万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650190/
关键词：
SEPARATED FLOW REATTACHED FLOW CONVECTION HEAT TRANSFER DIRECT NUMERICAL SIMULATION HORSESHOE VORTEX SURFACE-MOUNTED BODY 直接シミュレーヨン

项目摘要

Direct numerical simulation methodology has been employed to clarify the large scale vortex structure formed in the separated and reattached flow around the surface-mounted rectangular blocks and its correlation with the heat transfer mechanisms. The finite difference method is used to calculate the three-dimensional unsteady Navier-Stokes equations and the energy equation. The fifth-order upwind difference for the space derivative of convection terms is adopted to simulate minutely the detailed flow characteristics. Results obtained are summarized as follows.1. As for the single block, the number of horseshoe vortices formed around it increases from two to six with an increase of Reynolds number.2. In the case of two in-line blocks, the recirculation region extends the whole space between two blocks for small block space. Further, it is found that the horseshoe vortex is not formed around the second block even for a very wide space.3. The flow around two transversal blocks becomes similar to that around a single rectangular block at a very small transversal space, as illustrating a large single horseshoe vortex around them. As the space increases, two horseshoe vortices are formed around each block, they severely interact, and the flow between two blocks is very complicated.4. In the case of staggered three-row blocks, the flow in the neighborhood of the front and side surfaces of the first and second blocks is similar to that of the single block. The horseshoe vortex is formed around the third block only at Re= 500.5. As the Reynolds number increases up to 1000, the unsteadiness of flow becomes severe, as accompanying the shedding of large scale vortices from the blocks.6. These flow structures described briefly above bring about great variations of the heat transfer characteristics around the blocks.

采用直接数值模拟的方法，研究了矩形块体绕流分离和再附着过程中形成的大尺度涡结构及其与换热机制的关系。采用有限差分法求解三维非定常Navier-Stokes方程和能量方程。采用对流项空间导数的五阶迎风差分，对流动特性进行了细致的模拟。主要研究结果如下：1.对于单个块体，随着雷诺数的增加，其周围形成的马蹄涡数量从2个增加到6个.在两个串联块体的情况下，对于小块体空间，再循环区域延伸两个块体之间的整个空间。此外，还发现即使在很宽的空间内，第二块体周围也不会形成马蹄涡.在很小的横向间距下，两个横向块体的绕流变得类似于单个矩形块体的绕流，如在它们周围示出了大的单个马蹄形涡。随着间距的增大，每个块体周围形成两个马蹄涡，它们之间相互作用严重，块体间的流动非常复杂.在交错的三行块体的情况下，在第一和第二块体的前表面和侧表面附近的流动类似于单个块体的流动。马蹄涡仅在Re= 500.5时才在第三块体周围形成。当雷诺数增加到1000时，流动的非定常性变得严重，伴随着大尺度涡从块体上脱落.上面简要描述的这些流动结构导致块体周围的传热特性发生很大变化。