Research On Aerodynamic Characteristics Of Hypersonic Inlets With Dynamic/steady Angle-of-attack

The aerodynamic characteristic of hypersonic inlet with angle-of-attack is a major concern forresearchers because it has important theoretical and engineering background and it's closely related tothe performances of hypersonic vehicles. For the pitching attitude can be altered or forced tooscillation in the flight process of hypersonic vehicles, CFD simulation and wind tunnel experimentcombined with theoretical analysis was conducted to study the effect of dynamic/steadyangle-of-attack on hypersonic inlet in the present work. The flow-field features and performances ofhypersonic inlet are investigated and the mechanisms of the influences are discussed. The significanceof the current work is developing the research of hypersonic inlet at dynamic and steady conditionwith angle-of-attack and offer theoretical foundations for the design of effective control methods forhypersonic research vehicles.The performances of hypersonic inlet with angle-of-attack in steady-state are analyzed in thefirst part of paper. Four typical kinds of hypersonic inlet including2-D inlet, axisymmetric inlet, sidewall compression inlet and rectangular-to-circle shape transition (RCST) inlet designed in the sameconstraints are numerical investigated. The flow field feature and performances variation withangle-of-attack are revealed and the aerodynamic characteristics are investigated. It suggests that: Thecompression of hypersonic inlets, the boundary layer thickness and the flow quality into internalcompress tunnel are altered by the change of angle-of-attack then the flow capture characteristics andthe total pressure recovery coefficients of hypersonic inlet are affected. It is also found that the peakback-pressure endured by hypersonic inlet would increase and the starting ability would fall with therising of angle-of-attack. But the flow field characteristics and performance of axisymmetrichypersonic inlet is in completely different laws with other typical type of inlet configurations.In order to research how characteristic of hypersonic inlet response to rapid periodic dynamicangle-of-attack, unsteady CFD simulations and the Dynamic Mesh were employed and performed.The influence of different parameters on unsteady aerodynamic characteristics and the startingproblem caused by the angle-of-attack was analyzed. The result shows that: The unsteady flow fieldfeature and the performance of hypersonic inlet is lag behind of the steady cases for the hysteresiseffect caused by compressibility and viscous of air. The value of unstarting angle-of-attack wouldincrease while the restarting value would decrease with the rising of frequencies/angular velocity forthe aerodynamic delay caused by dynamic of angle-of-attack in hypersonic inlet starting process. Inaddition, the dynamic of angle-of-attack in specific rate and frequency can help the hypersonic inlet lacking of self-starting ability to restart because the movement of compress wedge change the externalflow feature. It also suggests that: the angular velocity, the frequency, the amplitude in oscillation,inflow Mach number and the Geometric scale of hypersonic inlet play an important role inaerodynamic characteristic while there are no significant influence with contrast ratio, flying altitude,CG location and the blunt at the front of inlet.The primary focus of the third part in this paper is on the2-D hypersonic inlet which isintegrated with forebody of hypersonic vehicle. The aerodynamic characteristic of the threedimensional integrated model inlet with dynamic angle-of-attack is investigated and predicted at flightcondition. The research carried out reveals that: The performance of integrated model inlet is also lagbehind of the steady cases for the hysteresis effect and there is also a delay in hypersonic inletunstarting and restarting process. For the integrated model of hypersonic forebody/inlet working atcruise and stage separation mode, there are no sudden changes in the performance parameters andworking mode caused by dynamic of angle-of-attack at certain amplitude.At the last part of this paper, several rapid periodic dynamic angle-of-attack wind tunnelexperiments are conducted at Mach3.85on2-D hypersonic inlet and sidewall compression inlet, therange of angle-of-attack is0~8.2°and the frequency is up to10.4Hz. As a result of wind tunnelexperiment, some conclusions can be drawn as follows: With the range of angle-of-attack, theoscillating2-D inlet works in starting mode; There are no significantly changes in performancesthroughout the oscillation and the parameters influenced are similar to steady cases. The sidewallcompression inlet goes through an unstart-restart process and a hysteresis effect is also found which ismore remarkable in time of inlet unstarting. The value of unstarting angle-of-attack would increaseand the restarting value would decrease with the rising of frequency in the oscillation that is alsofound in CFD simulation and confirmed by these wind tunnel experiments.The mechanisms of the influences caused by dynamic angle-of-attack are discussed, it suggeststhat: The appearance, development and disappearance of low Mach number region and separationnear solid wall is affected notability, which would alter the aerodynamic characteristic of hypersonicinlet. The difference between the unsteady generation and disappearance of the low Mach numberregion and the separation is the primary reason for the different aerodynamic characteristic ofhypersonic inlet with dynamic angle-of-attack.