FLUID-LOADED VIBRATION DUE TO A NON-HOMOGENEOUS TURBULENT BOUNDARY LAYER

Flow-induced structural acoustics involves the study of the vibration of a structure induced by a fluid flow as well as the resulting sound generated and radiated by the motion of the structure. A thin rectangular, structure, non-fluid-loaded was excited by turbulent boundary layer flow. A method called magnitude-phase identification (MPI) is derived to measure modal information from a structure using only two-point measurements. Using MPI, the mode shapes and the auto spectral density of vibration of each mode was measured and found to agree well with the theoretical values. When the non fluid-loaded structure was excited with a spatially non homogeneous wall pressure field or fluid-loaded structure was excited with a spatially homogeneous wall pressure field, the measured mode shapes were found to be the same as those predicted by theory. When a fluid-loaded structure was excited with a spatially non-homogeneous wall pressure field, the mode shapes were found to change. This suggests that standard modal analysis may not be sufficient to predict the vibration of fluid-loaded structures, as such theory assumes that the mode shapes of the structure are independent of the method by which the structure is excited.