Experimental study on transonic buffeting of launch vehicles with large-diameter fairing using elastic models

ifasd2024 Tracking Number 179

The launch vehicle may experience transonic buffeting during atmospheric ascent. Usually, fluctuation pressure wind tunnel testing with rigid model is performed to assess the buffeting loads. However, for the shapes prone to buffeting, such as the large-diameter fairing with a hammerhead nose shape, it is recommended by NASA SP8001 to use an elastic model to study their buffeting response and evaluate potential hazards. In this paper, a set of elastic models with same structural dynamic characteristics and different diameters of fairing were investigated for theirs transonic buffeting behaviours. These configurations with different fairing-core diameter ratios, which are 1.55, 1.60, and 1.73, respectively. The aeroelastic damping and buffeting load response characteristics of different diameter-ratio configurations were obtained by conducting aeroelastic damping tests and buffeting load response tests. From the aeroelastic damping test results, it is shown that the model with a diameter ratio of 1.60 exhibits negative aerodynamic damping at certain Mach numbers and Angle-of-Attack. Thus, solely from the perspective of aerodynamic damping, it is not possible to conclude that larger diameter ratios lead to instability or increased buffeting. However, from the buffeting load response test results, it is evident that with an increase in diameter ratio, the structural dynamic load response, in terms of both response amplitude and the Mach number range of significant amplitude, increases, especially for the 1.73 diameter ratio case. This implies that with larger diameter ratios, the buffeting response amplitude becomes more severe, and the duration of significant response increases. Therefore, for the transonic buffeting issue of launch vehicles with large-diameter fairings, evaluation should be conducted from both the perspectives of aeroelastic damping stability and buffeting response dynamic loads.