宽速域流动控制技术与气动特性
随着飞行器向高速、宽域、高机动和高隐身方向的发展，飞行器在高超或超声速流动中会面临流动不稳定和热防护等极端问题，直接影响到飞行器的整体性能。宽速域流动控制技术涉及在亚声速、跨声速、超声速乃至高超声速等广泛速度范围内，对流体流动进行精确控制的技术。在宽速域流动控制技术的研究中，气动特性是一个重要的研究方向，可以为飞行器的设计、优化和控制提供重要依据。宽速域条件下的流动控制技术和气动特性研究对于提升飞行器的性能、稳定性和可靠性至关重要，成为当前航空航天技术的核心内容之一。本专题涉及宽速域中的流动控制技术、气动特性等方面的领域，旨在为高超声速飞行器设计和应用提供新的思路和技术支持，推动航空航天推进技术的发展。
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2024, 46(2):49-61.
DOI: 10.11887/j.cn.202402005
Abstract:
Starting from the mechanism of SWTBLI(shock wave/turbulent boundary layer interaction) and the urgent need for flow control, the research progress of the adaptive control techniques in the SWTBLI from four aspects was summarized, namely adaptive vortex generator, adaptive bump, adaptive micro jets and adaptive secondary recirculation jet. Analysis shows that developing adaptive flow control techniques, combined with AI technology, and accelerating intelligent control schemes can be used as an important technical means for wide-speed flight of the new generation hypersonic vehicle. Specifically, it is to realize local flow acceleration/deceleration, aerodynamic thermal protection, aerodynamic control and other functions in different areas of the hypersonic vehicle by adjusting external excitation, and to establish a control feedback loop according to flow field parameters, so it can adaptively adjust the structure of the local flow field to meet the actual needs of engineering.
Starting from the mechanism of SWTBLI(shock wave/turbulent boundary layer interaction) and the urgent need for flow control, the research progress of the adaptive control techniques in the SWTBLI from four aspects was summarized, namely adaptive vortex generator, adaptive bump, adaptive micro jets and adaptive secondary recirculation jet. Analysis shows that developing adaptive flow control techniques, combined with AI technology, and accelerating intelligent control schemes can be used as an important technical means for wide-speed flight of the new generation hypersonic vehicle. Specifically, it is to realize local flow acceleration/deceleration, aerodynamic thermal protection, aerodynamic control and other functions in different areas of the hypersonic vehicle by adjusting external excitation, and to establish a control feedback loop according to flow field parameters, so it can adaptively adjust the structure of the local flow field to meet the actual needs of engineering.
2023, 45(6):40-47.
DOI: 10.11887/j.cn.202306005
Abstract:
The analysis and design method of the sky-ground scaled similarity of aerodynamic characteristics for stratospheric airship were described in detail. The similarity criteria for the rigid and flexible models to complete the wind tunnel tests were given. Two kind of scaled models and wind tunnel test were completed. By analyzing the wind tunnel experimental data for scaled models, it was found that the aerodynamic characteristics of the stratospheric airship under different inflatable internal pressures were basically same, but the rigid body model was obviously different. The aerodynamic drag coefficient under flexible characteristics was significantly higher than that of rigid body, and even twice as high as that under zero attack angle, which lead to the essential changes of the rolling aerodynamic torque characteristics, such as stability and divergence. It has important engineering application value for evaluating flexible aerodynamic characteristics of stratospheric airship, especially under low pressure state. And it overcomes the disadvantages of using rigid body aerodynamic characteristics data or engineering estimation method in the airship overall design of "dynamic-resistance balance".
The analysis and design method of the sky-ground scaled similarity of aerodynamic characteristics for stratospheric airship were described in detail. The similarity criteria for the rigid and flexible models to complete the wind tunnel tests were given. Two kind of scaled models and wind tunnel test were completed. By analyzing the wind tunnel experimental data for scaled models, it was found that the aerodynamic characteristics of the stratospheric airship under different inflatable internal pressures were basically same, but the rigid body model was obviously different. The aerodynamic drag coefficient under flexible characteristics was significantly higher than that of rigid body, and even twice as high as that under zero attack angle, which lead to the essential changes of the rolling aerodynamic torque characteristics, such as stability and divergence. It has important engineering application value for evaluating flexible aerodynamic characteristics of stratospheric airship, especially under low pressure state. And it overcomes the disadvantages of using rigid body aerodynamic characteristics data or engineering estimation method in the airship overall design of "dynamic-resistance balance".
2022, 44(5):180-186.
DOI: 10.11887/j.cn.202205019
Abstract:
The Fay-Riddell correlation, direct simulation Monte Carlo method, and the Fourier heat transfer expression based on direct simulation Monte Carlo flow field temperature were considered. Cases with different freestream Knudsen numbers (Kn) and Mach numbers (Ma) were studied to provide a new understanding of the classical continuum method to overestimate the stagnation point heat flux in the rarefied region from the microscopic perspective. The related results show that the rarefied effect on the stagnation point heat flux includes three aspects. The temperature jump upon the wall decreases the temperature gradient, reducing the stagnation point heat flux. The translational nonequilibrium was found near the wall, which leads to the failure of the Fourier heat conduction law and overestimates the heat flux. The wall-bound effect makes the Fourier heat conduction law overestimates the heat flux located three times the mean free path away from the wall.
The Fay-Riddell correlation, direct simulation Monte Carlo method, and the Fourier heat transfer expression based on direct simulation Monte Carlo flow field temperature were considered. Cases with different freestream Knudsen numbers (Kn) and Mach numbers (Ma) were studied to provide a new understanding of the classical continuum method to overestimate the stagnation point heat flux in the rarefied region from the microscopic perspective. The related results show that the rarefied effect on the stagnation point heat flux includes three aspects. The temperature jump upon the wall decreases the temperature gradient, reducing the stagnation point heat flux. The translational nonequilibrium was found near the wall, which leads to the failure of the Fourier heat conduction law and overestimates the heat flux. The wall-bound effect makes the Fourier heat conduction law overestimates the heat flux located three times the mean free path away from the wall.
2022, 44(1):92-98.
DOI: 10.11887/j.cn.202201014
Abstract:
The numerical method was used to study the aerodynamic flow field characteristics of hypervelocity projectiles, especially in the reentry phase. The prediction accuracy of S-A and k－ω SST turbulence model was verified by wind tunnel test data. The calculation results show that the prediction accuracy of the two turbulence models is higher than 2% in normal force prediction. In axial force prediction, the S-A turbulence model has a high prediction accuracy of 4.6%. When the projectile reenters at a large angle of attack, the transverse flow effect of projectile is more obvious. The shock wave makes the surface pressure of the projectile increase sharply on the windward side, while the large-scale streamwise vortex structure formed on the leeward side reduces the pressure, and the increase of the pressure on the windward side has a greater impact on the aerodynamic coefficient of projectile. The aerodynamic drag and lift coefficient at high angle of attack are obviously nonlinear, the drag coefficient is obviously increased, and the static stability margin is also sharply reduced, which makes the convergence characteristics of projectile worse, and that is treated as the main reason for the velocity attenuation during the reentry process of projectile.
The numerical method was used to study the aerodynamic flow field characteristics of hypervelocity projectiles, especially in the reentry phase. The prediction accuracy of S-A and k－ω SST turbulence model was verified by wind tunnel test data. The calculation results show that the prediction accuracy of the two turbulence models is higher than 2% in normal force prediction. In axial force prediction, the S-A turbulence model has a high prediction accuracy of 4.6%. When the projectile reenters at a large angle of attack, the transverse flow effect of projectile is more obvious. The shock wave makes the surface pressure of the projectile increase sharply on the windward side, while the large-scale streamwise vortex structure formed on the leeward side reduces the pressure, and the increase of the pressure on the windward side has a greater impact on the aerodynamic coefficient of projectile. The aerodynamic drag and lift coefficient at high angle of attack are obviously nonlinear, the drag coefficient is obviously increased, and the static stability margin is also sharply reduced, which makes the convergence characteristics of projectile worse, and that is treated as the main reason for the velocity attenuation during the reentry process of projectile.
2022, 44(4):101-115.
DOI: 10.11887/j.cn.202204011
Abstract:
The numerical simulation method was used to carry out a systematic study on the roll control of the flying wing using the trailing-edge CC(circulation control) jet at a wide speed range (Ma为0.145～0.7), and was compared with the configuration controlled by classical control surfaces. Research focuses the electromagnetic stealth characteristics, the roll control characteristics and their flow physics, and the impacts of the bleed air. Results show that as the Mach number increases, the roll control capability of the CC jet decreases due to the weakening of entrainment and blocking effects. However, the CC jet enhances the stealth performance at specific azimuth ranges remarkably. Moreover, it requires less bleed air, induces less thrust loss, and has a high control efficiency factor (aerodynamic moment coefficient produced per unit of additional drag coefficient). In conclusion,the trailing-edge CC jet is a highly promising roll control device for a flying wing.
The numerical simulation method was used to carry out a systematic study on the roll control of the flying wing using the trailing-edge CC(circulation control) jet at a wide speed range (Ma为0.145～0.7), and was compared with the configuration controlled by classical control surfaces. Research focuses the electromagnetic stealth characteristics, the roll control characteristics and their flow physics, and the impacts of the bleed air. Results show that as the Mach number increases, the roll control capability of the CC jet decreases due to the weakening of entrainment and blocking effects. However, the CC jet enhances the stealth performance at specific azimuth ranges remarkably. Moreover, it requires less bleed air, induces less thrust loss, and has a high control efficiency factor (aerodynamic moment coefficient produced per unit of additional drag coefficient). In conclusion,the trailing-edge CC jet is a highly promising roll control device for a flying wing.
2020, 42(3):66-73.
DOI: 10.11887/j.cn.202003009
Abstract:
In order to study the impact of different ejecting state on aerodynamic heating of hypersonic aircrafts,the square/circle hole ejecting under hypersonic flow condition was numerically simulated. The impacts of ejecting pressure, ejecting velocity and ejecting direction to the main flow field were discussed and the flow field structure, wall heat flux and center line temperature at different ejecting state were obtained. The results show that gas ejection can relieve the aerodynamic heating situation of wall to some extent. The cooling effect at whole wall ejection is remarkable. And the wall heat flux reduces nearly two-thirds when the ejecting velocity is about 1 m·s-1. Moreover, at high ejecting velocity (Ma>1), the cooling effect is strengthened by increasing the ejecting pressure and velocity appropriately. At low ejecting velocity (Ma<0.6), the ejection flows within the boundary layer, and has a weak influence on the main flow field structure; the greater the ejecting velocity is, the bigger the range of cooling is, and the better the cooling effect is. The cooling effect of downstream is better when the ejecting direction is acute angle, and the cooling effect of upstream is better when the ejecting direction is obtuse angle.
In order to study the impact of different ejecting state on aerodynamic heating of hypersonic aircrafts,the square/circle hole ejecting under hypersonic flow condition was numerically simulated. The impacts of ejecting pressure, ejecting velocity and ejecting direction to the main flow field were discussed and the flow field structure, wall heat flux and center line temperature at different ejecting state were obtained. The results show that gas ejection can relieve the aerodynamic heating situation of wall to some extent. The cooling effect at whole wall ejection is remarkable. And the wall heat flux reduces nearly two-thirds when the ejecting velocity is about 1 m·s-1. Moreover, at high ejecting velocity (Ma>1), the cooling effect is strengthened by increasing the ejecting pressure and velocity appropriately. At low ejecting velocity (Ma<0.6), the ejection flows within the boundary layer, and has a weak influence on the main flow field structure; the greater the ejecting velocity is, the bigger the range of cooling is, and the better the cooling effect is. The cooling effect of downstream is better when the ejecting direction is acute angle, and the cooling effect of upstream is better when the ejecting direction is obtuse angle.
2019, 41(1):101-107.
DOI: 10.11887/j.cn.201901015
Abstract:
Aiming at the modeling problem of hypersonic gliding missile tracking, a method of aerodynamic parameter model based on the law of guidance variables was studied. The aerodynamic parameters were analyzed and the shortcomings of the traditional modeling method were pointed out. With the assumption that the guidance variables obey the first-order delay process, the aerodynamic parameter model was derived by using the linearized aerodynamic coefficients. By analyzing the variants of model under different flight conditions, the model adaptability for target′s maneuver was proved. The values of unknown parameters were discussed, so as to realize the adaptive matching of model with flight state. Simulation results show that the performance of the proposed model is obviously better than the traditional model when the target is maneuvering. Simultaneously, the simulation under different filter parameters confirms the model′s validity.
Aiming at the modeling problem of hypersonic gliding missile tracking, a method of aerodynamic parameter model based on the law of guidance variables was studied. The aerodynamic parameters were analyzed and the shortcomings of the traditional modeling method were pointed out. With the assumption that the guidance variables obey the first-order delay process, the aerodynamic parameter model was derived by using the linearized aerodynamic coefficients. By analyzing the variants of model under different flight conditions, the model adaptability for target′s maneuver was proved. The values of unknown parameters were discussed, so as to realize the adaptive matching of model with flight state. Simulation results show that the performance of the proposed model is obviously better than the traditional model when the target is maneuvering. Simultaneously, the simulation under different filter parameters confirms the model′s validity.
2018, 40(6):17-22.
DOI: 10.11887/j.cn.201806003
Abstract:
In order to investigate the differences of the transition mechanisms between four roughness shapes, a fifth-order WCNS scheme was used to simulate the supersonic flat-plate boundary layer transition induced by the square, cylinder, diamond and hemisphere roughness elements at Mach 4.20. Results show that the square roughness element has the longest separated region where the absolute instability is formed, thus resulting in the earliest transition. The diamond roughness element has the widest separated region and leads to the widest turbulent wake region. The cylinder and hemisphere roughness elements are less effective in inducing transition compared with the square and diamond roughness elements.
In order to investigate the differences of the transition mechanisms between four roughness shapes, a fifth-order WCNS scheme was used to simulate the supersonic flat-plate boundary layer transition induced by the square, cylinder, diamond and hemisphere roughness elements at Mach 4.20. Results show that the square roughness element has the longest separated region where the absolute instability is formed, thus resulting in the earliest transition. The diamond roughness element has the widest separated region and leads to the widest turbulent wake region. The cylinder and hemisphere roughness elements are less effective in inducing transition compared with the square and diamond roughness elements.
2016, 38(5):99-104.
DOI: 10.11887/j.cn.201605016
Abstract:
According to the trajectory tracking problem of hypersonic glide vehicle under great deviation conditions, a new adaptive tracking guidance method in the injection phase was put forward based on the adaptively revised weighting matrix. The main control mode and standard trajectory characteristics were analyzed. The simplified longitudinal motion equations were linearized near the standard trajectory. An improved adaptive tracking guidance method was designed by introducing the error term in linear quadratic performance index. The simulation results of CAV-H indicate that this method can achieve a great performance in adaptive tracking guidance in the injection phase, and has a good robustness to the initial and process deviation.
According to the trajectory tracking problem of hypersonic glide vehicle under great deviation conditions, a new adaptive tracking guidance method in the injection phase was put forward based on the adaptively revised weighting matrix. The main control mode and standard trajectory characteristics were analyzed. The simplified longitudinal motion equations were linearized near the standard trajectory. An improved adaptive tracking guidance method was designed by introducing the error term in linear quadratic performance index. The simulation results of CAV-H indicate that this method can achieve a great performance in adaptive tracking guidance in the injection phase, and has a good robustness to the initial and process deviation.
2016, 38(2):48-55.
DOI: 10.11887/j.cn.201602009
Abstract:
Numerical studies on a spatially developing supersonic mixing layer were performed by means of large-eddy simulation. Focusing on the effect of transverse forcing on the passive scalar mixing characteristic of mixing layer. The results for the baseline case without external forcing are in agreement with the analytical evidence. Afterwards, the effect of transverse forcing on the scalar structure, scalar thickness and volumetric entrainment ratio of mixing layer were analyzed. Results indicate that the frequency and amplitude of transverse forcing alter the growth rate and entrainment ratio of the passive scalar mixing significantly. High-frequency forcing magnifies the scalar thickness and volumetric entrainment ratio in the near field of mixing layer. However, the growth rate in the far field is increased by the low-frequency forcing. The entrainment ratio is, to be a large extent, dominated by the large-scale eddy entrainment process. The multiple-frequency forcing seems to validly enhance the scalar mixing in supersonic mixing layer.
Numerical studies on a spatially developing supersonic mixing layer were performed by means of large-eddy simulation. Focusing on the effect of transverse forcing on the passive scalar mixing characteristic of mixing layer. The results for the baseline case without external forcing are in agreement with the analytical evidence. Afterwards, the effect of transverse forcing on the scalar structure, scalar thickness and volumetric entrainment ratio of mixing layer were analyzed. Results indicate that the frequency and amplitude of transverse forcing alter the growth rate and entrainment ratio of the passive scalar mixing significantly. High-frequency forcing magnifies the scalar thickness and volumetric entrainment ratio in the near field of mixing layer. However, the growth rate in the far field is increased by the low-frequency forcing. The entrainment ratio is, to be a large extent, dominated by the large-scale eddy entrainment process. The multiple-frequency forcing seems to validly enhance the scalar mixing in supersonic mixing layer.
2014, 36(2):30-33.
DOI: 10.11887/j.cn.201402006
Abstract:
The design of a blockage adjustor at the exit is commonly used in simulating the impacts of backward pressure on the isolator flow field. Numerical simulation was adopted to study the effects of different block modes. Three modes were compared, including installing a flat on the ramp side wall, a flat on the cowl side wall and a wedge in the middle of the flow field. The results show that due to the asymmetric boundary layer on the ramp wall and cowl wall, the shock trains formed by them are all next to the cowl side. The intensity of the shock train generated by the second mode is stronger and the boundary layer separates more evidently, which chocks the isolator more easily and poses difficulty for the study of shock train in experiment. The other two modes can generate similar flow field, but the first one can be realized more easily.
The design of a blockage adjustor at the exit is commonly used in simulating the impacts of backward pressure on the isolator flow field. Numerical simulation was adopted to study the effects of different block modes. Three modes were compared, including installing a flat on the ramp side wall, a flat on the cowl side wall and a wedge in the middle of the flow field. The results show that due to the asymmetric boundary layer on the ramp wall and cowl wall, the shock trains formed by them are all next to the cowl side. The intensity of the shock train generated by the second mode is stronger and the boundary layer separates more evidently, which chocks the isolator more easily and poses difficulty for the study of shock train in experiment. The other two modes can generate similar flow field, but the first one can be realized more easily.
2014, 36(2):73-80.
DOI: 10.11887/j.cn.201402013
Abstract:
The injection, mixing and atomization characteristics of transverse liquid jet in liquid-fueled scramjet are the determining factors for the efficiency of the combustion chamber. An origin image analysis method, without any threshold choosing section, was developed in house to get the unique unstable boundary of the transverse jet without any manual effects. The lateral extension boundary capturing method, which is based on PIV technique and the corresponding image analysis method, was developed to illustrate the lateral outer boundary of the jets. Results from targeted and comparative experiments indicate that, compared with the single jet case, the penetration heights and lateral extension become larger in the assemble jets cases. A larger distance between the streamwise assembled double injectors contributes to a higher penetration height of the jet.
The injection, mixing and atomization characteristics of transverse liquid jet in liquid-fueled scramjet are the determining factors for the efficiency of the combustion chamber. An origin image analysis method, without any threshold choosing section, was developed in house to get the unique unstable boundary of the transverse jet without any manual effects. The lateral extension boundary capturing method, which is based on PIV technique and the corresponding image analysis method, was developed to illustrate the lateral outer boundary of the jets. Results from targeted and comparative experiments indicate that, compared with the single jet case, the penetration heights and lateral extension become larger in the assemble jets cases. A larger distance between the streamwise assembled double injectors contributes to a higher penetration height of the jet.
2013, 35(5):1-5.
Abstract:
Through combining an experiment and a numerical simulation, a study was carried out on supersonic mixing layer with splitters of different geometric configurations, which is under the condition of Ma1=1.5，Ma2=2.5，T0,1=300K，T0,2=1200K，and matched pressure p1=p2=86kPa.In the experiment, it was discovered that the thickness of mixing layer in the flow field with splitters in which a cavity is mounted grows as the ratio of the length to the depth of the cavity becomes larger; Splitters with sawtooth trail show great effect of mixing enhancement and making the flow field highly unsteady. In the numerical study, it was demonstrated that the mixing-enhancement effect of splitters with cavity is due to the cavity shear layer’s reattachment to the trail of the splitter, and splitters with sawtooth trail due to induced large-scale streamwise vortexes.
Through combining an experiment and a numerical simulation, a study was carried out on supersonic mixing layer with splitters of different geometric configurations, which is under the condition of Ma1=1.5，Ma2=2.5，T0,1=300K，T0,2=1200K，and matched pressure p1=p2=86kPa.In the experiment, it was discovered that the thickness of mixing layer in the flow field with splitters in which a cavity is mounted grows as the ratio of the length to the depth of the cavity becomes larger; Splitters with sawtooth trail show great effect of mixing enhancement and making the flow field highly unsteady. In the numerical study, it was demonstrated that the mixing-enhancement effect of splitters with cavity is due to the cavity shear layer’s reattachment to the trail of the splitter, and splitters with sawtooth trail due to induced large-scale streamwise vortexes.
