Wilkes Daniel R, Peters Herwig, Croaker Paul, Marburg Steffen, Duncan Alec J, Kessissoglou Nicole
Centre for Marine Science and Technology, Department of Imaging and Applied Physics, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia.
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, New South Wales 2052, Australia.
J Acoust Soc Am. 2017 Jun;141(6):4278. doi: 10.1121/1.4983686.
The non-negative intensity (NNI) method is applied to large-scale coupled fluid-structure interaction (FSI) problems using the fast multipole boundary element method (FMBEM). The NNI provides a field on the radiating structure surface that consists of positive-only contributions to the radiated sound power, thus avoiding the near-field cancellation effects that otherwise occur with the sound intensity field. Thus far the NNI has been implemented with the boundary element method (BEM) for relatively small problem sizes to allow for the full BEM coefficient and inverse matrices to be explicitly constructed and stored. In this work, the FMBEM is adapted to the NNI by calculating the eigenvalue solution of the symmetric acoustic impedance matrix using the FMBEM via a two-stage solution method. The FMBEM implementation of the NNI is demonstrated for a large-scale model of a submerged cylindrical shell. The coupled FSI problem is first solved using a finite element-FMBEM model and the resulting surface fields are then used in the FMBEM calculation of the NNI. An equivalent reactive NNI field representing the evanescent near-field radiation is demonstrated and the effect of the chosen number eigenvectors on the NNI field is investigated.
非负强度（NNI）方法通过快速多极边界元法（FMBEM）应用于大规模流固耦合（FSI）问题。NNI在辐射结构表面提供一个场，该场仅由对辐射声功率的正向贡献组成，从而避免了声强场中否则会出现的近场抵消效应。到目前为止，NNI已与边界元法（BEM）一起用于相对较小的问题规模，以便能够显式构建和存储完整的BEM系数和逆矩阵。在这项工作中，通过使用两阶段求解方法，利用FMBEM计算对称声阻抗矩阵的特征值解，使FMBEM适用于NNI。针对一个大型水下圆柱壳模型展示了NNI的FMBEM实现。首先使用有限元-FMBEM模型求解耦合的FSI问题，然后将得到的表面场用于NNI的FMBEM计算。展示了一个表示消逝近场辐射的等效电抗NNI场，并研究了所选特征向量数量对NNI场的影响。
