对轴向磁场作用下的流致振动问题进行数值研究，应用有限元方法模拟磁场和圆柱-柔性薄梁振动共同作用下金属流体速度场，分析磁场强度和柔性薄梁长度对柔性薄梁振幅、振动频率以及流场流动特性的影响。结果表明：柔性薄梁在绕流脱涡作用下做周期性振动，其主导振型与欧拉-伯努利梁的一阶固有模态相似。随着磁场强度增加，流场非定常流动将被抑制，柔性薄梁振幅减小；柔性薄梁长度增加将使振动频率减小，振幅呈先增大后减小的非线性关系。对于流场脱涡特性，磁场强度增加促进涡的耗散，降低涡脱落频率；柔性薄梁长度越长，其与圆柱绕流剪切层相互作用时的能量耗散越大，显著改变了脱涡模式，从脱涡流态转变为稳定流态的临界哈特曼数随柔性薄梁长度增加而减小。

This paper conducts a numerical study on the problem of flow-induced vibration under an axial magnetic field. The finite element method is used to simulate the velocity field of the metal fluid under the combined effects of the magnetic field and the vibration of a cylinder-flexible beam. This research analyzes the influence of magnetic field intensity and flexible beam length on the amplitude， vibration frequency of the flexible beam， and the flow characteristics of the flow field. The results indicate that the flexible beam undergoes periodic vibrations due to vortex shedding effects， and the dominant vibration mode exhibits a close resemblance to the first-order natural mode of an Euler-Bernoulli beam. As the magnetic field intensity increases， the unsteady flow in the flow field is suppressed， resulting in a decrease in the amplitude of the flexible beam. Increasing the length of the flexible beam decreases the vibration frequency， while the amplitude shows a nonlinear relationship that first increases and then decreases. Regarding the vortex shedding characteristics of the flow field， an increase in magnetic field intensity promotes vortex dissipation， and reduces the frequency of vortex shedding. Additionally， the longer the flexible beam， the greater the energy dissipation during its interaction with the cylinder shear layer， which significantly changes the vortex shedding pattern； the critical Hartmann number for the transition from vortex shedding flow to steady flow decreases with the increase in the flexible beam length.