Dependence On Reynolds Number Of Wake Structure Of A Square Cylinder

There are various applications of flow around square cylinders in real life, such as water flows past the pier, offshore platform and fluid around high buildings, etc. When the fluid flows past the bluff body, the vortices are alternatively shed and the alternate shedding of vortices may cause structural vibration, acoustic noise emissions and resonance due to the associated forces on the body. This phenomenon can lead the failure of structure and economic losses. The wake structure of a circular has been achieved a lot of attentions, but very less for a square cylinder. According to this situation, the thesis pays attention to the wake structure of a square cylinder. The formation length, wake width, transition length and drag coefficients are measured.The turbulence characteristics of flow past a square cylinder have been investigated in the large Reynolds number(Re) range of 75 ~ 5.75 × 104 by using experimental and numerical methods. The flow for Re = 75 ~ 200 and Re = 200 ~ 1.4 × 103 are simulated using laminar model and κ-ω SST model, respectively. The experimental work is carried out in an open-circuit wind tunnel using hot-wire anemometer and particle images velocimetry(PIV) for flow visualization. The formation length and wake width of the flow near square cylinder are obtained by results of simulation and PIV experiments. In the range of Reynolds numbers greater than 1.4 × 103 the position of the shear layer of transition to turbulence is studied using hot-wire anemometry. It is found that the transition point moves towards the cylinder with increasing Reynolds number which shows general agreement with precious study of flow around a circular cylinder.