Numerical analysis of transonic buffet flow around a hammerhead payload fairing

During ascent of launcher, the unsteady aerodynamic loads associated with transonic buffet flow have become of considerable concern. To study the unsteady dynamics of buffet flow, delayed detached-eddy simulations of a hammerhead configuration have been conducted at transonic Mach numbers. The results, including mean Cp, Cp_rms, PSD and Schlieren visualizations, were validated by the measurements obtained from the wind-tunnel experiments. Nevertheless, to perform a good validation for unsteady loads, the numerical data needed to be filtered according to the data acquisition used in the experiments. The studies were performed by means of instantaneous, statistical, spectral and cross-spectral analysis of the numerical data, which identify the fluid dynamic mechanism that produces a relatively strong buffet environment. The mechanism involves a sequence of vortex, which is shed downstream, merges together, and ultimately impinges on the wall leading to large fluctuations. Besides, the cross-spectral analysis also revealed that the subsequent large scale and low frequency vortex shedding of the developed shear layer provides a strong influence on the flows around cone–cylinder conjunction. The fluctuations in this area are highly sensitive to Mach numbers, and the peak of Cp_rms appears at Ma ≈ 0.81.