Numerical study of unsteady shock/boundary-layer interaction induced by a blunt fin

Unsteady three-dimensional shock/turbulent boundary layer separations induced by a hemicylindrically blunted fin normal to the flat plate considering the sweepback angle are numerically studied. It is known by previous experimental studies that those flows become unsteady. However, unsteady flow characteristics dominating them have not been captured sufficiently by previous numerical studies yet. In the present study, the higher-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme with the modified AUSM and the maximum second-order LUSGS scheme are employed to get unsteady flows associated with the shock/turbulent boundary layer interaction and shock/shock interference between the separation shock and the bow shock. In the calculated results of the unswept fin, unsteady multiple supersonic jets are produced by the interaction between multiple separation shocks and the bow shock. A large-scale supersonic jet induced by multiple jets streams into separation bubbles. The number of bubbles is changed according to the strength and the direction of the jet. Each bubble generates a separation shock. Therefore, a system of multiple separation shocks is formed again. Finally, this cyclic system makes the present flow unsteady and intermittent. The cases of the swept fin are also calculated. The reduction of the separation length and the stabilization of the unsteadiness can be explained by the strength of the cyclic system.