二维方柱绕流阻塞效应的大涡模拟

Large Eddy Simulation of Blockage Effect on Flow Past a Two Dimensional Square Cylinder

摘要:

在均匀流条件下对阻塞比(R）分别为4.2%、10%、16.7%、20%和25%的二维方柱绕流进行了大涡模拟（LES）研究，对比了各工况下柱体的整体气动力和表面风压分布随阻塞比的变化规律，分析了阻塞比对柱体附近区域内流场特性和瞬时涡量的影响.研究表明，当阻塞比由4.2%增大到25%，柱体的平均阻力系数、脉动升力系数和Strouhal数分别增加了27.6%、43.6%和31%.随着阻塞比的增大，侧面及背风面负风压系数的均值绝对值以及脉动值均显著增加，柱体两侧附近流场特性也有明显的变化.在大阻塞比工况中，洞壁附近会生成二次旋涡，并与柱体脱落的旋涡相互掺混.

关键词:风洞试验; 阻塞比; 大涡模拟; 气动力; 瞬时涡量

Abstract:

The uniform flow past two dimensional square cylinders with blockage ratios 4.2%, 10%, 16.7%, 20% and 25% were numerically investigated by largeeddy simulation (LES). The aerodynamic forces and pressure distributions of the cylinders with these blockage ratios were discussed. The blockage effects on flow field characteristics and instantaneous vorticity were investigated. The results show that when the blockage ratio increases from 4.2% to 25%, the average drag coefficient， fluctuating lift coefficient and Strouhal number increase by 27.6%, 43.6% and 31%, respectively. The mean suction pressure coefficients and fluctuating pressure coefficients on the side and leeward surfaces of the cylinder both increase with the blockage ratios. The blockage effects on the flow characteristics around the cylinders are significant. Furthermore, for high blockage ratios, periodic and alternating vortices are observed in the vicinity of the walls and mix with the vortices shedding from the cylinders.

Key words:wind tunnel test; blockage ratio; large eddy simulation; aerodynamic forces; instantaneous vorticity