Research On Aerodynamic Characteristics Of Lateral Jet In Hypersonic Flow By The DSMC Method

The Reaction Control System(RCS)is widely used in attitude and orbit control of various aircrafts.The control force mainly comes from the counterforce induced by the lateral jet.When aircrafts fly in a rarefied atmosphere,the rarefied multiscale effect should not be ignored.Also the effect of real gas should be taken in to account in the prediction of aerodynamic characteristics as the flight Mach number is over 6~8.Therefore,it is necessary to research the mechanism of the interaction between the rarefied effect and the real-gas effect in the jet interaction flow field and explore the influence of the mechanism on the RCS efficiency.In this paper,the direct simulation of Monte-Carlo method(DSMC)with Q-K model is employed to investigate lateral jet interaction with hypersonic free stream for its advantage in simulating multiscale flow field.Different cases are calculated to validate reliability the chemical model and the accuracy of the DSMC-QK algorithm.The hypersonic flow over a compression ramp is also studied by the method to test its ability in capturing multiscale flow characters and to research the relation between the flow structure and the aerodynamic characteristics.Moreover,the DSMC-QK algorithm is used to predict the latera jet interaction flow field on twodimension/ three-dimension flat plate model and slender revolution body.The effect of different flight altitude,freestream Mach number and the momentum flux ratio are studied.The main results is as follows.Firstly,the research indicates that as the flight height and the rarefied effect increase,the separation zone which is closely related to the surface pressure coefficient contract when the flight Mach number is relatively low(7ma).So the area of the high pressure region before the jet decrease.As a result,the force amplification factor and moment amplification factor decrease and the center of pressure moves upstream.The jet control efficiency decreases.With the increasing of the flight Mach number,surface pressure coefficient in the wake region rise apparently,which makes the amplification factors and the control efficiency increase.At the same time,the real-gas effect become obvious in high Mach number condition,which results in negative effect on aerodynamic interference-induced forces.Secondly,the rarefied effect and the real-gas effect exist at the same time in real flight.On one hand,the rarefied effect weakens the chemical reactions between gas molecules.On the other hand,the influence area of the chemical reactions on the vehicle surface diminishes with the contraction of the separation zone.Together,the influence of the real-gas effect on control efficiency decreases with the increasing of altitude.Finally,the variation trend of amplification factors with flight altitude in high flight Mach number(20ma)differs from that of comparative low Mach number.This attributes to the increasing contribution to aerodynamic interference-induced forces in the wake region.As the negative influence of real-gas effect on interference-induced forces weakens with the increasing of altitude,the degree the amplification factors decreasing is reduced.Thus,the changing of aerodynamic characteristics and jet control efficiency is influenced by the interaction of flow structures,the rarefied effect and the real-gas effect.