图9. 当$\theta = 60^ \circ$时,主圆柱升力与位移的相位差($\phi _{ly} )$、升力均方根($C'_{\rm L} )$、振幅($A^ * )$以及能量系数($E_{\rm c1},E_{\rm c2},E_{\rm c}$分别为主圆柱、两附加小圆柱以及总能量系数)随折合流速变化情况

Fig.9. The phase difference between the lift and displacement ($\varphi _{ly} )$, the r.m.s. lift coefficient ($C'_{\rm L} )$, the vibration amplitude ($A^ * )$ of the main cylinder, and energy transfer coefficient ($E_{\rm c1}$,$E_{\rm c2}$,$E_{\rm c}$ denote the energy coefficients of the main, two small, and the sum of three cylinders, respectively.) in one period versus the reduced velocity at$\theta = 60^ \circ$