NUMERICAL INVESTIGATION ON UNSTEADY FLOW FROM HYPERSONIC TWO-WEDGE SEPARATION

Hypersonic multi-body vehicles are often considered a viable option for reusable space-access transportation systems due to their advantages, such as low cost and high efficiency. Among various separation strategies, hypersonic aft ejection separation represents an important research direction. Under hypersonic conditions, the multi-body separation process typically involves complex shock interactions, which directly affect separation safety and attitude stability. In this study, the hypersonic aft ejection separation process is simplified as an inviscid flow around two wedges in tandem configuration. Numerical simulations are conducted to investigate the dynamic separation process of the two wedges under a Mach 7 freestream. The motion of the separating body is handled using the overset dynamic grid technology and is determined by the coupled solution of the fluid governing equations and the three-degree-of-freedom rigid-body dynamics equations. The study focuses on analyzing the motion behavior and aerodynamic characteristics of the separating body under different masses and initial lateral separation velocities. It clarifies the evolution of the unsteady shock structures during separation and explores the interplay mechanisms among the unsteady shock structures, the aerodynamic characteristics, and the motion behavior of the separating body. It is found that the separating body exhibits four typical motion modes relative to the leading body: escape, return, shock surfing, and reversal. Except for the reversal case, as the mass (or initial separation velocity) decreases, the trajectory of the separating body gradually approaches the leading body's forward shock. During the process of passing through the leading body's attached shock, the flow field around the separating body sequentially experiences shock-expansion wave interference and shock-shock interference. The intense shock interactions near its lower surface lead to a sharp increase in aerodynamic forces. After successful separation, the windward-side shock of the separating body alternates between an attached shock and a detached bow shock, resulting in periodic oscillations in aerodynamic forces. Specifically, the drag and lift coefficients exhibit periodic variations resembling cosine- and sine-like functions, respectively.