RESPONSE OF STRUCTURE TO THE PSEUDO-SOUND FIELD OF A JET (USING A COMBINED CONTINUUM AND FINITE ELEMENT METHOD) PART I

Prediction techniques are applied to a typical aircraft panel mounted along, and just outside of the wake of a model jet. From measurements made, a functional representation of the pseudo-sound wall pressure correlation is obtained and is used to predict the response characteristics of the panel. The predicted mean square response is in fair agreement with the measured values, but the predicted displacement spectra are somewhat erroneous. However, this was expected. The upper frequency limit of the finite element technique is restricted by the number of elements in the grid system, above which response predictions incur ever increasing error in both frequency and amplitude. However, at these higher mode numbers the continuum technique becomes increasingly more accurate due to the decreasing dependence of modal frequency and shape on the panel edge conditions. It was deduced that in the case of a simple panel, excited by the pressure field of a full scale jet engine only the power spectrum is required to predict the response. However, for a complex structure, spatial decay becomes relevant and must be included in the pressure field model. (Author)