# Aerodynamic Characteristics of Supersonic Rocket-Sled Involving Waverider Geometry
## 1 Introduction
Many researchers have conducted numerical simulations for supersonic rocket-sleds [7; 8; 9; 10]. In our previous work [11], numerical investigations of the supersonic axisymmetric base flow at Mach number 2.46 and Reynolds number 2.858 \(\times\) 10\({}^{6}\) were carried out using a scale-adaptive simulation (SAS) approach. We found that there was no large-scale vortex shedding phenomenon, so vortex shedding was not the main factor causing vibration. In later studies, we identified some shockwave oscillation patterns of two common rocket-sleds through numerical simulation [12]. This work provides the basis for further investigation into supersonic rocket-sleds. The Holloman test center found that the sled would resonate with the track at a certain speed. The results showed that the three resonance factors were shockwaves, vortex shedding and the excitation source of position, with shockwaves being the most important factor [13]. A large quantity of test data has shown that the vibration of the rocket-sled would be gradually intensified with increase in running speed. Several failed tests showed that such adverse vibration could threaten the safety of rocket-sled tests [13]. The existing rocket-sled consumes the vibration energy by adding damping devices such as springs. [PERSON] et al. [14] proposed a soft structure connecting the rocket-sled and the rails to improve the vibration environment of the rocket-sled. This kind of damping device corresponds to passive damping and was found not to be sufficiently effective. In addition, the introduction of smoother rails and sliders was only able to reduce the vibration caused by random contact of sled rails and had little effect on aerodynamic vibration. Thus, a new approach to solving the problem of aerodynamic vibration of rocket-sleds is needed. The aerodynamic vibration of a rocket-sled mainly comes from the conical shockwave and its reflected shockwave. If the generation of shockwaves is eliminated or suppressed, the vibration of the rocket-sled will be greatly reduced. Therefore, it is necessary to adopt some effective flow control methods. Flow control methods can be divided into active control methods and passive control methods [15; 16; 17; 18; 19; 20]. Table 1 shows several common active and passive flow control methods. Because active flow control can be adjusted according to feedback, its control effect is better when the environment is changeable. However, the principle and structure of active control are often very complicated, which sometimes makes its application difficult. The ability of passive control to adapt to external changes is poor, but its application is relatively simple. Shockwave control methods include changing geometric parameters, blowing suction flow and changing fluid properties. Among these, changing geometric parameters is a common method, which achieves its purpose by optimizing the shape or inclination angle [21]. If the formation and propagation direction of the shockwave can be controlled by changing the shape of the head and body of the rocket-sled, the intensity of the reflected shockwave can be weakened, and the influence of aerodynamic excitation vibration can also be reduced. Waveider is a special shape designed to improve the lift-to-drag ratio of supersonic aircraft, which, in essence, is a form of aerodynamic shape optimization. Its leading edge generates attached shockwaves due to its special configuration and can block the flow of air above and below [41; 42]. The hypersonic testing center in the University of Maryland conducted a great deal of experimental and theoretical research on the waverider, and developed the first waverider design and optimization software \"MAXWARP\". This software can generate the corresponding waverider according to the design conditions [43]. [PERSON] et al. [44] proposed a simple analytical model for parametric design of a supersonic waverider, which can easily and quickly obtain the waverider under specific conditions and conduct performance optimization.