横流向热浮升力对并列双圆柱流致振动的影响

Effects of crossflow thermal buoyancy on flow-induced vibration of side-by-side cylinders

采用浸入边界法对横流向热浮升力作用下并列双圆柱的流致振动进行数值模拟研究。详细总结了理查森数Ri=3条件下并列双圆柱的最大振幅、时均位移、升阻力系数、频率特性和尾流模式等随间距比及折合流速的变化规律。研究发现:在横流向热浮升力作用下,并列双圆柱振幅和升、阻力系数呈现不对称特点,振动响应除出现涡激振动外,在更高折合流速下出现驰振;圆柱振动平衡位置相对其初始位置均发生与热浮升力反向的偏移,偏移量随折合流速增大而增加;在涡振阶段,并列双圆柱尾流场表现出稳定的宽窄尾流模式,两个圆柱的泄涡基本保持反相同步;在驰振阶段,尾流场表现为同相同步模式,圆柱的振动响应出现了倍频锁定现象。

Here,the immersed boundary method was used to numerically simulate flow-induced vibration of side-by-side cylinders under the action of crossflow thermal buoyancy.Variations of maximum amplitude,time-average displacement,lift and drag coefficients,frequency characteristics and wake mode of side-by-side cylinders with changes of spacing ratio and reduced velocity under Richardson number Ri=3 were summarized in detail.The results showed that amplitude,lift and drag coefficients of side-by-side cylinders are asymmetric under the action of crossflow thermal buoyancy;in addition to vortex-induced vibration appearing,galloping occurs at higher reduced velocity;equilibrium position of cylinder vibration is offset from its initial position in opposite direction to that of thermal buoyancy lift,and offset increases with increase in reduced velocity;in vortex-induced vibration stage,wake flow fields of side-by-side cylinders have stable wide-narrow wake mode,and vortex shedding leakages of side-by-side cylinders basically keeps opposite phase synchronization;in galloping stage,wake flow fields are in-phase synchronization mode,and vibration responses of side-by-side cylinders have phenomenon of superhar monic lock-in.