Acoustic-Fluid-Structure Interaction (AFSI) in the Car Underbody 2022-01-0938

The turbulent flow around vehicles causes high amplitude pressure fluctuations at the underbody, consisting of both hydromechanic and acoustic contributions. This induces vibrations in the underbody structures, which in turn may lead to sound transmission into the passenger compartment, especially at low frequencies. To study these phenomena we present a run time fully coupled acoustic-fluid-structure interaction framework expanding a validated hybrid CFD-CAA solver. The excited and vibrating underbody is resembled by an aluminium plate in the underbody of the SAE body which allows for sound transmission into the interior.

Different excitation situations are generated by placing obstacles at the underbody upstream of the aluminium plate. For this setup we carry out a fully coupled simulation of flow, acoustics and vibration of the plate. The simulation results are compared and validated with experimental results of surface microphones, acceleration measurements and sound spectra of the interior. The analysis of the results focuses on the ratio of hydromechanic and acoustic excitation in frequency space and on possible back coupling effects of the structural vibration on the results. In the outlook, one example of an application of this method in the vehicle development is given.