SOUND GENERATION BY UNSTEADY FLOW ABOUT A RECTANGULAR CUBOID

Flow past a rectangular brick yawed at 30 degrees to the streamwise direction is simulated using a hybrid lattice gas - lattice Boltznann computational fluid dynamics code. This simple geometric shape generates vortex shedding similar to that found on a vehicle greenhouse, or upper, glass-containing portion of an automobile. This simulation computes the time-accurate flow field in order to capture the unsteady surface pressure which is the primary source of vehicle aerodynamic noise. The timeaveraged flow field closely matches the experimentally observed steady-state field. The surface pressure spectra for locations on the top surface of the brick are computed for frequencies between 50 and 5000 Hz. The shapes of the computed sound spectra compare well with the experimental data for locations clearly inside the two vortex regions or in the reattached flow region, but need a 15 dB shift to match the sound pressure level absolutely. The spectra for monitoring locations in the flow reattachment region compare less closely to experimental data.