ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

1pNS8. Acoustic radiation prediction of an engine block using a combined finite element method and boundary element method technique integrated with test data.

Ralph Garcea

LMS N. America, 5455 Corporate Dr., Ste. 303, Troy, MI 48098

The project discussed in this paper was undertaken to validate the acoustic radiation prediction of engine block noise using a combined FEM and BEM technique, integrated with experimental data. Using a strictly analytical technique, the acoustic results from a BEM analysis will be limited by the accuracy of the velocity boundary conditions generated from structural FEM data. Experimentally determined velocity boundary conditions are more accurate, but they may not be available at every node of the BEM mesh. A new tool has been developed that combines the calculated structural modes of vibration with a limited set of measurement data, to extrapolate velocity boundary conditions on the entire BEM model. A FEM technique is used for the structural analysis and an indirect BEM technique is used to predict noise at some distance from the engine block. Very good correlation is obtained with measured sound-pressure levels. The modal expansion procedure combines experimental and numerical data to provide more velocity boundary conditions for the BEM acoustic analysis. Incorporating the test data helps to define a more realistic excitation and damping in the model, leading to more accurate noise predictions.