Global stability of hypersonic flow over a spherically blunted double cone

The influence of nose radius on hypersonic flows over a canonical 25°–55° double-cone configuration is investigated across a series of bluntness ratios and Reynolds numbers in this study. The base-flow results demonstrate that increasing the nose radius can substantially alter the shock interaction structures. The length of the separation zone is almost invariant up to a critical nose radius, beyond which it undergoes a remarkable increase followed by a gradual decrease. The global stability analysis reveals a similar non-monotonic trend in the global instability of the double-cone flow. As the nose radius increases, the double-cone flow initially becomes more unstable and then tends to be more stabilized beyond a critical value. The features of unstable modes captured by the global stability analysis show good agreement with the data of direct numerical simulations. The three-dimensionality is found to be induced by the global instability. These findings suggest that an appropriate blunting of the leading-edge can effectively mitigate the flow separation and stabilize the hypersonic double-cone flows.