Shear Effects on Flow past a Square Cylinder at Moderate Reynolds Numbers
by Shuyang Cao, (corresponding author), M.ASCE, (Professor, State Key Lab for Disaster Reduction in Civil Engineering, Tongji Univ., Siping Road 1239, Shanghai 200092, China. Email: caoshuyang@hotmail.com, shuyang@tongji.edu.cn), Yaojun Ge, (Professor, State Key Lab for Disaster Reduction in Civil Engineering, Tongji Univ., Siping Road 1239, Shanghai 200092, China.), and Yukio Tamura, M.ASCE, (Professor, Wind Engineering Research Center, Tokyo Polytechnic Univ., Iiyama 1583, Kanagawa 2430297, Japan.)
Journal of Engineering Mechanics, Vol. 138, No. 1, January 2012, pp. 116123, (doi: http://dx.doi.org/10.1061/(ASCE)EM.19437889.0000309)
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Document type: 
Journal Paper 
Abstract: 
Direct numerical simulation (DNS) and large eddy simulation (LES) with a dynamic Smagorinsky subgrid model are performed to investigate the flow past a square cylinder under the influence of velocity shear at the inlet at moderate Reynolds numbers (R=150–1,000). The shear rate is expressed by a dimensionless shear parameter β, which is based on the velocity gradient, side length of the cylinder, and upstream velocity at the center plane of the cylinder. Shear parameter varies from 0 to 0.2 in this study. Several Reynolds numbers are considered to study the Reynolds number dependence and the Strouhal number were found to have no significant variation with the shear parameter. The peak frequency of drag coefficient fluctuation becomes identical with that of the lift force coefficient when β>0.1. The vortices on the lowvelocity side disappear in the far wake under the strong shear condition. The stagnation point moves to the highvelocity side and the movement increases with an increase in shear parameter. An interesting finding is that the lift force acts from the lowvelocity to the highvelocity side, which is opposite to the case of a circular cylinder under the same inflow situation, whereas the drag force shows little variation with shear parameter. 
Author Keywords: 
 Aerodynamic force 
 Direct numerical simulation 
 Large eddy simulation 
 Shear parameter 
 Vortex shedding 
 Wake dynamics 
