To predict the dynamic response and acoustic radiation from an underwater structure, large impedance method was provided based on finite elemnt/ boundary element method, which uses the vibration data got from experiment as input. In the large impedance method, an imaginary element with large impedance was loaded at the test point. A force was supposed to act on the test point, which leads to the same vibration response at the test point as in test. The imaginary element may be of large mass or large grounded spring, which was chosen according to the item tested at the test point. Since the dynamic response is effected only by the response of the test point, the impedance of the main structure and the transfer impedance from the test point to the main structure, the driving source which is on the upstream of the test point needn't be built in the finite element model, which leads to great convenience in prediciton of dynamic response and acoustic radiation from an underwater structure. Dynamic response and acoustic radiation from a steel cylindrical model were predicted as an example by using the large impedance method. Comparisons of numerical results and experimental results show their good agreement and the large impedance method was validated.%为了满足水下结构振动与声学预报的需要,基于有限元/边界元法,采用以实测振动数据作为输入对水下结构振动与辐射噪声进行预报.预报采用大阻抗方法.使用大阻抗方法时,在建立结构有限元模型时,在振动测点建立一个虚构的单元,使得测点处具有很大的阻抗,并在测点施加一个相关的激振力,使得在该激振力的作用下测点处具有等于实测振动的响应,从而实现实测振动数据的输入.依据所测物理量的不同,大阻抗法可分为大质量方法和大刚度方法.如果测点振动响应能够完全描述测点“上游”激振源特性,则无须考虑测点“上游”的激振设备相关参数,这为水下结构振动与辐射噪声预报提供了便利.采用大阻抗方法,对钢质柱壳单点激振模型进行了计算和比较,数值结果同试验结果比较表明两者吻合很好；对多点多自由度激振力激振模型进行了核算,证实大阻抗方法能有效地实现以实测振动数据为输入的水下结构振动与辐射噪声预报.
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