A Switching-Based Interference Control for Booster Separation of Hypersonic Vehicle

Whether launching from the ground or in the air, hypersonic vehicles need the booster to accelerate to a predetermined window, so as to meet the requirements of scramjet engine ignition. Therefore, there is interference suppression between boosters and hypersonic vehicles under the high dynamic pressure, which has become a key technical problem that affects the success of flight tests, especially when the aircraft is statically unstable. A method of variable structure switching-based control is proposed in this paper for rapid suppression on hypersonic vehicle booster separation interference. Switching control systems in real time according to state changes caused by flow field interference, the method can keep the attitude stability of hypersonic vehicle booster separation under the high dynamic pressure of static instability. The aerodynamic calculation model of the hypersonic vehicle booster separation process is established first, which adopts an unsteady solution and clarifies the aerodynamic interference characteristics of the afterbody on the vehicle in booster separation. Then, according to the characteristics of the flow field, the dynamics of the vehicle in and out of the interference area are converted into subsystems with switching characteristics. Using the dimension reduction and variable structure method, the switching control surface of the control system is established. On the basis of the vehicle state changes caused by flow field, the control system on the orbital change surface can be switched in real time to achieve stable attitude in the process of separation interference. Meanwhile, considering the additional interference torque generated by the afterbody to the vehicle in the separation process, a control system for interference suppression of the booster separation is designed. Simulation results verify that the designed control system can rapidly suppress the booster separation interference when the dynamic pressure is about 150 kPa and the vehicle has the static instability of 5%, thereby realizing the stable attitude of the vehicle.

Large Eddy Simulation of Hypersonic Turbulent Boundary Layers

The recent revival of interest in developing new hypersonic vehicles brings attention to the need for accurate prediction of hypersonic flows by computational methods. One of the challenges is prediction of aerothermodynamic loading over the surface of the vehicles. Reynolds Average Navier-Stokes (RANS) methods have not shown consistent accuracy in prediction of such flows. Therefore, new methods including Large Eddy Simulations (LES) should be investigated. In this paper, the LES method is used for prediction of the boundary layer over a flat plate. A new recycling-rescaling method is tested. The method uses total enthalpy and static pressure along with the velocity components to produce the best results for the Law of the Wall, turbulent statistics and turbulent Prandtl number.