A mathematical model for a rotated triangular tube array with 7 rigid-body degrees of freedom subject to two-phase flow and loose support was presented to study the two-phase flow-induced instability and nonlinear dynamics in the parallel direction. To verify the correctness of this model, an experiment was carried out to obtain the Hopf bifurcation velocities of fluidelastic instability of a rotated triangular tube array with the pitch-to-diameter ratio is 1.48 for five void fraction conditions. Then, considering the effects of the impact stiffness forces between the tube bundles and the tube support plates, the Hopf bifurcation and the nonlinear dynamics of a rotated triangular tube array within 0%, 20%, 40%, 60%, and 80% void fraction conditions were calculated. The numerical results show that when the flow pitch velocity increases beyond the Hopf bifurcation velocity, the periodic motion occurs. At a sufficiently high flow pitch velocity, some complex motions of the tube bundles such as the multi-frequency motion, the chaotic motion may occur. And, the effects of the void fraction on the bifurcation characteristic of the tube bundles were also investigated.

提出了一个具有7个刚体自由度的旋转三角管阵列的数学模型，该阵列受两相流和松动支撑的作用，研究了两相流在平行方向上引起的不稳定性和非线性动力学。为了验证该模型的正确性，进行了一项实验，以求得在五个空隙率条件下，螺距与直径之比为1.48的旋转三角管阵列的流体弹性不稳定性的Hopf分叉速度。然后，考虑管束和管支撑板之间的冲击刚度力的影响，霍夫夫分叉和旋转三角管阵列在0％，20％，40％，60％和80％空隙内的非线性动力学计算馏分条件。数值结果表明，当水流速度增加超过霍普夫分叉速度时，就会发生周期性运动。在足够高的水流速度下，管束的某些复杂运动（例如多频运动）可能会发生混乱。并且，还研究了空隙率对管束的分叉特性的影响。