圆角化对受迫振动方柱绕流特性影响机理分析

为分析圆角化对低雷诺数下受迫振动方柱绕流特性的影响机理, 对Ansys Fluent软件进行二次开发, 即通过用户自定义函数中的DEFINE_ CG_MOTION宏对柱体周期性受迫振动的函数进行编程, 并对流场计算域进行区域划分以便利用动网格技术中动态层法实现柱体受迫振动, 从而实现对受迫振动柱体绕流流场的流固耦合模拟.在雷诺数Re = 200时, 考虑方柱截面不同圆角的影响, 对均匀流作用下5种圆角化r/D = 1/2, 1/4, 1/5, 1/8和0受迫振动方柱的绕流进行数值模拟, 分析了这5种参数下受迫振动方柱的升阻力系数、尾流涡量和锁定区间的变化规律, 澄清了圆角化对受迫振动方柱稳定性的影响机理.研究表明: 与尖角方柱相比, 圆角化方柱升阻力系数有了明显的减小, 且升力、阻力系数随圆角增大而减小; 低振幅比下圆角方柱的涡旋脱落模式均为2S模态, 涡旋尾迹变窄; 锁定区间范围基本关于F = 1对称, 锁定区间的变化趋势与圆柱类似. 

MECHANISM ANALYSIS ON THE EFFECT OF CIRCULARIZATION ON THE WINDING CHARACTERISTICS OF A FORCED VIBRATING SQUARE COLUMN

In order to analyze the effect mechanism of circularization on the winding characteristics of the forced vibrating square column at low Reynolds number, the secondary development of Ansys Fluent software was carried out to program the periodic forced vibration of the column, that is, the DEFINE_ CG_MOTION macro in the user-defined function (UDF) was used, and the computational domain of the flow field was divided into some regions in order to realize the forced vibration of the column by using the dynamic layer method in the dynamic grid technique, so as to realize the simulation of the fluid-solid coupling of the column-wound flow field. At Reynolds number Re = 200, considering the influence of different rounding angles of the square column cross-section, numerical simulation was made for the flow around five forced vibration square columns with rounded corners r/D = 1/2, 1/4, 1/5, 1/8 and 0 under uniform flow, and the variation laws of the drag coefficient, eddy volume and locking interval of the forced vibrating square column under these five parameters were analyzed to clarify the effect mechanism of circularization on the stability of the forced vibrating square column. It is shown that the lift and resistance coefficients of the rounded square column are significantly reduced with increasing rounded angle compared with the sharp-angled square column; the vortex shedding mode of the rounded square column under low amplitude ratio is 2S mode, and the vortex trails become narrower; the locking interval range is basically symmetric about F = 1, and the trend of the locking interval is similar to that of the cylinder.