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.