| Because of the practical importance and the wealth of interesting fluid flow phenomena, much progress has been made in understanding of the flow around a square cylinder placed near a wall. However, due to its physical complexity, the experimental results of unsteady characteristics and a complete and conclusive explanation of the physics are still lacking. The use of advanced techniques in experiments and data post-processing methodologies has made it possible to enhance our knowledge of the phenomenon.In the present work, detailed results of time averaged flow properties as well as unsteady flow characteristics in the near wake of a square cylinder with side length D placed near a wall are measured in a low-speed water tunnel. Particle image velocimetry(PIV) and time-resolved particle image velocimetry(TR-PIV) measurements are conducted for cylinder to wall gap heights, G, from G/D=0.1 to G/D=1.0.The PIV measurements obtain some time-mean results such as velocity field, recirculation length and shear stress distribution. According to the comparison of these results in different kinds of G/D, the influence of wall proximity on vortex shedding and flow characteristics in the wake is clarified, as well as a critical gap height of 0.3D is deduced. For 0.3 |
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