Assessing Low Frequency Flow Noise Based on an Experimentally Validated Modal Substructuring Strategy Featuring Non-Conforming Grids

The continuous encouragement of lightweight design in modern vehicles demands a reliable and efficient method to predict and ameliorate the interior acoustic comfort for passengers. Due to considerable psychological effects on stress and concentration, the low frequency contribution plays a vital rule regarding interior noise perception. Apart other contributors, low frequency noise can be induced by transient aerodynamic excitation and the related structural vibrations. Assessing this disturbance requires the reliable simulation of the complex multi-physical mechanisms involved, such as transient aerodynamics, structural dynamics and acoustics. The domain of structural dynamics is particularly sensitive regarding the modelling of attachments restraining the vibrational behaviour of incorporated membrane-like structures. In a later development stage, when prototypes are available, it is therefore desirable to replace or update purely numerical models with experimental data. To this end, an original strategy has therefore been developed to estimate the vibro-acoustic response due to aerodynamic excitation based on a modal coupling approach. The incorporated acoustic and structural modes can be obtained either from numerical models or through experimental modal analysis. The presented work begins with the principles of modal vibro-acoustic substructuring and the practical workflow employed. Its applicability is demonstrated by an experimentally validated automotive structure subject to transient aerodynamic load.