A new approach to identify buffet loads for aircraft vertical tail

It is difficult to perform direct measurement of the buffet loads acting on the vertical tail of an aircraft. This paper presents a novel frequency domain approach to identify buffet loads point by point from the measured acceleration responses. Based on the statistical property of the buffet loads in the time domain and spatial domain, the buffet loads are expressed as a linear combination of orthogonal functions in the spatial domain and random functions in the time domain. The spatial function is composed of a set of orthogonal functions, and the identification of buffet loads in the frequency domain is transformed into the estimation of the time function. First, the relationship between the acceleration spectral density and the generalized exciting force spectral density is obtained from the aeroelastic motion equation of the vertical tail; then, the relationship of the exciting force spectral density and buffet loads spectral density is obtained in terms of spectral decomposition. The time function can be identified utilizing the orthogonality of the spatial functions point by point. In order to address ill-posedness, a new regularization process is introduced to guarantee the stability of identification, and the optimal regularization factor is selected by Newton's iteration. A vertical tail model is adopted to verify the feasibility and precision of the proposed method. A set of buffet loads are simulated by a computational fluid dynamics (CFD) code, and these buffet loads are exerted on the vertical tail to calculate the corresponding buffeting acceleration responses which are used to identify the buffet loads using the proposed method. Good agreements between the calculated buffet loads and estimated buffet loads validate the present method.