Abstract:

In order to investigate the characteristics of flow past bluff bodies, an open water tunnel which appears to the flow condition is designed, the PIV(particle image velocimetry) and dyeing methods are introduced to complete the flow visualization. Insight 4 G software can take control of the experimental process strictly. The stability of the experimental apparatus is proved by detecting the flow state on laser plane at different heights in the water channel. The instantaneous flow in different Reynolds number and the periodic characteristic visualization at Re=200 for single cylinder are carried out to validate the correctness of visualization method. Flow field characteristics of circular and square cylinder under the condition of different Reynolds number have been revealed. Comparing the image with the existing simulation and experimental results verifies the accuracy of the particle image velocimetry and dyeing method. Analyze the difference and connection of the flow characteristics of circular and square cylinder to find the universal law and difference in flow past single bluff bodies. In the periodic flow past a cylinder experiment,the periodic rotation of positive and negative vortexes appear alternately. In a cycle, the positive vortexes are gradually formed, enhanced and dissipated, the negative vortexes are also developed in the corresponding position. Flow around a single circular cylinder has no fixed separation point while flow around a single square cylinder has fixed separation point before or after the sharp edges.

Key words: PIV, transition, flow, circular cylinder structure, square cylinder structure

摘要：

为解明钝体绕流机理，设计了开式低速循环水槽，建立了钝体绕流实验平台。采用粒子图像测速法（PIV）和染色法，对钝体绕流特性进行实验研究。采用INSIGHT 4 G进行全面调控。通过检测水槽不同高度激光面上的流动状态验证实验台稳定性。将PIV及染色法所得数据与已有模拟及实验结果进行对比，验证了实验方法正确性。选取过渡流下特定钝体（圆柱）进行周期研究，探寻钝体绕流周期性。并分析圆柱、方柱绕流在不同Reynolds数下的流动特性异同。实验表明：Re=200时，在一个周期内，圆柱周围正涡、负涡周期性脱落，正涡逐渐形成、增强、消散，负涡也在对应的位置循环发展。通过圆、方柱流动实验对比可知，圆柱绕流分离点不固定而方柱绕流分离点固定，位于其前后锐边上。

关键词: 粒子图像测速, 过渡, 流动, 圆柱, 方柱