Puri S., Morrey D., Bell A., Rudnyi E., Korvink J.

In a modern passenger vehicle, the noise, vibration and harshness (NVH) performance is one of the key parameters which the customer uses in determining product quality. As a result, engineers often seek to evaluate the low frequency NVH behaviour of vehicle interiors using coupled finite element-finite element (FE/FE) or finite element-boundary element discretized models. Due to the coupling between the fluid and structural domains in the coupled FE/FE formulation, the resulting mass and stiffness matrices are no longer symmetrical. Such a multi disciplinary approach requires the solution of these coupled fluid and structural equations, causing an inevitable increase of computational time and expense. Furthermore, this presents a major problem where optimization is required. In order to reduce the computational time of such coupled problems, engineers often use the mode superposition or the component mode synthesis method. However, the reduction is substantially smaller. This paper focuses on the application of Krylov based model order reduction (MOR) techniques to undamped fully coupled structural-acoustic models. The basic idea behind model reduction is to find a lower dimensional subspace, which well approximates the transfer function moments at certain points in the frequency domain. This is achieved using the open-source software mor4ansys, which performs model order reduction via the Arnoldi process from extracted ANSYS finite element matrices. As a test case, a harmonic simulation of clamped aluminium plate backed by a rigid walled cavity in the frequency range of 0-300Hz. is presented. The noise transfer functions inside the box are computed using both reduced and ANSYS models. The results from the reduced model are in good agreement with that of the higher dimensional ANSYS model. The test cases show a significant reduction of computational time required. The accuracy of the approach, cost/time reductions and future work in this area are discussed.