Hypersonic air-breathing propulsion is one of the key techniques for future aviation and the ground aerodynamic testing for full scale test models with sufficient test time at flight conditions is of fundamental impor...Hypersonic air-breathing propulsion is one of the key techniques for future aviation and the ground aerodynamic testing for full scale test models with sufficient test time at flight conditions is of fundamental importance for verifying hypersonic air-breathing engines.Based on the backward detonation-driven concept,the hypersonic flight-duplicated shock tunnel(or JF-12 shock tunnel)has been successfully constructed and calibrated.This facility is capable of reproducing airflow for Mach numbers ranging from 5 to 9 at an altitude of 25-50 km,with a test duration of more than 100 ms.To quantify the performance of the shock tunnel,experiments were conducted to investigate the aerodynamic characteristics of the test flows and the effects of several critical techniques that play important roles in the operation of the shock tunnel.The stagnation pressure was constant within士5%and the average stagnation pressure varied by less than 0.048%/ms.The variation of the stagnation pressure in repeated experiments is less than 2.0%,indicating the good repeatability of the wind tunnel.The non-uniformity of the Mach number in the core flow field at the nozzle exit was within士2.5%.Additional,a uniform flow field is established upstream of the nozzle exit.The axial gradients of the flow field are small since the Mach number varies less than 1.7%/m.Findings regarding the ignition technology,diaphragm ruptures,detonation driver capacity,incident shock-wave decay,and tunnel operation mode are also presented.The findings of this study are not only helpful for operating the shock tunnel,but can also assist the future development of hypersonic wind tunnels.展开更多
The nonlinear analyses of the hypersonic and high-enthalpy boundary-layer transition had received little attention compared with the widely-studied linear instabilities.In this work,the oblique-mode breakdown,as one o...The nonlinear analyses of the hypersonic and high-enthalpy boundary-layer transition had received little attention compared with the widely-studied linear instabilities.In this work,the oblique-mode breakdown,as one of the most available transition mechanisms,is studied using the nonlinear parabolized stability equations(NPSE)with consideration of the thermal-chemical non-equilibrium effects.The flow over a blunt cone is computed at a free-stream Mach-number of 15.The rope-like structures and the spontaneous radiation of sound waves are observed in the schlieren-like picture.It is also illustrated that the disturbances of the species mass and vibrational temperature near the wall are mainly generated by the product term of the wall-normal velocity disturbance and the mean-flow gradient.In comparison to the CPG flow,the TCNE effects destabilize the second mode and push upstream the N factor envelope.The higher growth rate of the oblique wave leads to stronger growth of the streamwise vortices and harmonic waves.展开更多
This article reviews the instrumental developments accomplished at ONERA in order to perform precise non-intrusive measurements of hypersonic flows using laser- and electron-beam-based optical techniques. Point line o...This article reviews the instrumental developments accomplished at ONERA in order to perform precise non-intrusive measurements of hypersonic flows using laser- and electron-beam-based optical techniques. Point line of sight and imaging measurements are possible. Point measurements have been implemented with Electron Beam Fluorescence （EBF） using detection of X-ray radiation and Coherent anti-Stokes Raman Scattering （CARS）. When spatial resolution is not required, diode laser absorption spectroscopy yields results integrated along a line. EBF imaging using a high energy pulsed electron gun is also quite promising. Rotational and vibrational populations of nitrogen and nitric oxide have been measured in various hypersonic hyperenthalpic facilities, as well as rotational state-resolved velocities in shocks and boundary layers.展开更多
Developing the waverider based hypersonic vehicles is an inverse design process in which shape is developed from a known flow field by tracing of streamlines to form a stream surface. The flow field can be based on a ...Developing the waverider based hypersonic vehicles is an inverse design process in which shape is developed from a known flow field by tracing of streamlines to form a stream surface. The flow field can be based on a solution of Taylor Maccoll equation for a specified shock or cone angle. This Paper discusses the development of waverider shapes for hypersonic reentry vehicles.展开更多
In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerody...In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerodynamic performance by both simulations and experiments.The basic flow field employed by proposed method is a combined flow named IBB,which is combined by Internal Conical Flow A(ICFA),truncated Busemann flow I(BI)for external section,and truncated Busemann flow II(BII)for internal section.The model configuration is generated by streamline tracing method from basic flow field,in which the forebody section is traced from ICFA and BI flows,and the inlet as well as strut section is traced from BII flow.The simulations in Mach number 4,5,and 6 demonstrate uniform starting flow fields with relatively high total pressure recovery,which agree well with experiments in wind tunnel.Additionally,in low Mach number cases,this inlet could start at Mach number 3 while it is unstarted at Mach number 2.7;in high Mach number cases,a uniform flow could still exist in Mach number 6.5 while a relatively strong shock wave boundary layer interaction is found in cowl area of Mach number 7 case,indicating the inlet designed by proposed method works in a relatively wide Mach number range.展开更多
A physical mechanism by which nose bluntness suppresses second-mode instability is proposed.Considered are 7 degree half-angle straight cones with nose bluntness radii of 0.15 mm, 3.556 mm,5 mm, 9.525 mm, 12.7 mm and ...A physical mechanism by which nose bluntness suppresses second-mode instability is proposed.Considered are 7 degree half-angle straight cones with nose bluntness radii of 0.15 mm, 3.556 mm,5 mm, 9.525 mm, 12.7 mm and 25.4 mm at tunnel conditions relevant to the AFOSR-Notre Dame Large Mach 6 Quiet Tunnel. It is shown that second-mode suppression is achieved via entropy layer modulation of the basic state density gradient. A weakening of the density gradient disrupts the acoustic resonance necessary to sustain second-mode growth. These results are consistent with the thermoacoustic interpretation which posits that second-mode instability can be modeled as thermoacoustic resonance of acoustic energy trapped within an acoustic impedance well.Furthermore, the generalized inflection point criterion of Lees and Lin is applied to develop a criterion for the existence of second-mode instability based on the strength of the basic state density gradient.展开更多
The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably...The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably involved in a global strike mission.Of the many direct methods,Gauss pseudospectral method（GPM）has been demonstrated as an effective tool to solve the trajectory optimization problem with typical constraints.However,a series of diffculties arises for complex constraints,such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones.The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and nofly zone constraints.Three kinds of specifc breaks are introduced to divide the full trajectory into multiple phases.The continuity conditions are presented to ensure a smooth connection between each pair of phases.Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique.Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with waypoint and no-fly zone constraints.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grants 11602275 and 11532014)。
文摘Hypersonic air-breathing propulsion is one of the key techniques for future aviation and the ground aerodynamic testing for full scale test models with sufficient test time at flight conditions is of fundamental importance for verifying hypersonic air-breathing engines.Based on the backward detonation-driven concept,the hypersonic flight-duplicated shock tunnel(or JF-12 shock tunnel)has been successfully constructed and calibrated.This facility is capable of reproducing airflow for Mach numbers ranging from 5 to 9 at an altitude of 25-50 km,with a test duration of more than 100 ms.To quantify the performance of the shock tunnel,experiments were conducted to investigate the aerodynamic characteristics of the test flows and the effects of several critical techniques that play important roles in the operation of the shock tunnel.The stagnation pressure was constant within士5%and the average stagnation pressure varied by less than 0.048%/ms.The variation of the stagnation pressure in repeated experiments is less than 2.0%,indicating the good repeatability of the wind tunnel.The non-uniformity of the Mach number in the core flow field at the nozzle exit was within士2.5%.Additional,a uniform flow field is established upstream of the nozzle exit.The axial gradients of the flow field are small since the Mach number varies less than 1.7%/m.Findings regarding the ignition technology,diaphragm ruptures,detonation driver capacity,incident shock-wave decay,and tunnel operation mode are also presented.The findings of this study are not only helpful for operating the shock tunnel,but can also assist the future development of hypersonic wind tunnels.
基金supported by the National Numerical Wind-tunnel projectThe authors also gratefully acknowledge the financial support of the National Key Research and Development Plan of China through the project No.2019YFA0405201the National Key Project(Grant No.GJXM92579).
文摘The nonlinear analyses of the hypersonic and high-enthalpy boundary-layer transition had received little attention compared with the widely-studied linear instabilities.In this work,the oblique-mode breakdown,as one of the most available transition mechanisms,is studied using the nonlinear parabolized stability equations(NPSE)with consideration of the thermal-chemical non-equilibrium effects.The flow over a blunt cone is computed at a free-stream Mach-number of 15.The rope-like structures and the spontaneous radiation of sound waves are observed in the schlieren-like picture.It is also illustrated that the disturbances of the species mass and vibrational temperature near the wall are mainly generated by the product term of the wall-normal velocity disturbance and the mean-flow gradient.In comparison to the CPG flow,the TCNE effects destabilize the second mode and push upstream the N factor envelope.The higher growth rate of the oblique wave leads to stronger growth of the streamwise vortices and harmonic waves.
文摘This article reviews the instrumental developments accomplished at ONERA in order to perform precise non-intrusive measurements of hypersonic flows using laser- and electron-beam-based optical techniques. Point line of sight and imaging measurements are possible. Point measurements have been implemented with Electron Beam Fluorescence （EBF） using detection of X-ray radiation and Coherent anti-Stokes Raman Scattering （CARS）. When spatial resolution is not required, diode laser absorption spectroscopy yields results integrated along a line. EBF imaging using a high energy pulsed electron gun is also quite promising. Rotational and vibrational populations of nitrogen and nitric oxide have been measured in various hypersonic hyperenthalpic facilities, as well as rotational state-resolved velocities in shocks and boundary layers.
文摘Developing the waverider based hypersonic vehicles is an inverse design process in which shape is developed from a known flow field by tracing of streamlines to form a stream surface. The flow field can be based on a solution of Taylor Maccoll equation for a specified shock or cone angle. This Paper discusses the development of waverider shapes for hypersonic reentry vehicles.
基金supported by the National Natural Science Foundation of China(Nos.12072157,51776096)China Postdoctoral Science Foundation(Nos.2019TQ0147,2020M671472)。
文摘In this paper a novel design method of aerodynamic configuration is proposed to integrate forebody,strut and inlet for strutjet engine,and a model at design point of Mach number6 is generated to investigate the aerodynamic performance by both simulations and experiments.The basic flow field employed by proposed method is a combined flow named IBB,which is combined by Internal Conical Flow A(ICFA),truncated Busemann flow I(BI)for external section,and truncated Busemann flow II(BII)for internal section.The model configuration is generated by streamline tracing method from basic flow field,in which the forebody section is traced from ICFA and BI flows,and the inlet as well as strut section is traced from BII flow.The simulations in Mach number 4,5,and 6 demonstrate uniform starting flow fields with relatively high total pressure recovery,which agree well with experiments in wind tunnel.Additionally,in low Mach number cases,this inlet could start at Mach number 3 while it is unstarted at Mach number 2.7;in high Mach number cases,a uniform flow could still exist in Mach number 6.5 while a relatively strong shock wave boundary layer interaction is found in cowl area of Mach number 7 case,indicating the inlet designed by proposed method works in a relatively wide Mach number range.
基金support from the Air Force Office of Scientific Research(AFOSR)(Grant FA9550-20-10047)。
文摘A physical mechanism by which nose bluntness suppresses second-mode instability is proposed.Considered are 7 degree half-angle straight cones with nose bluntness radii of 0.15 mm, 3.556 mm,5 mm, 9.525 mm, 12.7 mm and 25.4 mm at tunnel conditions relevant to the AFOSR-Notre Dame Large Mach 6 Quiet Tunnel. It is shown that second-mode suppression is achieved via entropy layer modulation of the basic state density gradient. A weakening of the density gradient disrupts the acoustic resonance necessary to sustain second-mode growth. These results are consistent with the thermoacoustic interpretation which posits that second-mode instability can be modeled as thermoacoustic resonance of acoustic energy trapped within an acoustic impedance well.Furthermore, the generalized inflection point criterion of Lees and Lin is applied to develop a criterion for the existence of second-mode instability based on the strength of the basic state density gradient.
基金supported by Aviation Science Foundation of China(No.2011ZC13001 and 2013ZA18001)National Natural Science Foundation of China(Nos:60975073,61273349,61175109 and 61203223)Innovation Foundation of BUAA for PhD Graduates
文摘The reentry trajectory optimization for hypersonic vehicle（HV）is a current problem of great interest.Some complex constraints,such as waypoints for reconnaissance and no-fly zones for threat avoidance,are inevitably involved in a global strike mission.Of the many direct methods,Gauss pseudospectral method（GPM）has been demonstrated as an effective tool to solve the trajectory optimization problem with typical constraints.However,a series of diffculties arises for complex constraints,such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones.The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and nofly zone constraints.Three kinds of specifc breaks are introduced to divide the full trajectory into multiple phases.The continuity conditions are presented to ensure a smooth connection between each pair of phases.Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique.Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with waypoint and no-fly zone constraints.
