In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measur...In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section.展开更多
爆炸成型弹丸(explosively formed projectiles,EFP)的飞行稳定性直接决定弹丸撞靶的姿态、速度和密集度,进而影响EFP的侵彻性能。为了提升高超音速(Ma=4~7)EFP的侵彻威力,综述目前EFP的构型及飞行稳定性,建立了大长径比尾裙和褶皱尾翼...爆炸成型弹丸(explosively formed projectiles,EFP)的飞行稳定性直接决定弹丸撞靶的姿态、速度和密集度,进而影响EFP的侵彻性能。为了提升高超音速(Ma=4~7)EFP的侵彻威力,综述目前EFP的构型及飞行稳定性,建立了大长径比尾裙和褶皱尾翼EFP模型;构建并验证了EFP高超音速气动参数的数值计算方法。分析了尾翼式EFP的结构参数(齿根高、齿宽、实心率)对升阻力、压心和飞行稳定性等的影响规律,研究了结构不对称程度和滚转运动对尾裙和尾翼式EFP静态气动参数的影响规律。在此基础上,建立并验证了EFP飞行动力学微分方程,分析了结构非对称和滚转运动对弹道径向偏移量的影响;研究了药型罩材质对球形、尾裙式、尾翼式EFP长距离飞行速度降的影响,定量分析了飞行稳定性对EFP存速能力的影响。研究表明:常规尾翼弹飞行稳定性判据仍适用于EFP高超音速空气弹道;通过斜置褶皱尾翼产生较低速的滚转运动,可以显著提高非对称结构EFP的空气弹道密集度;优化后的尾翼式EFP在飞行稳定性良好的同时,具有优异的存速能力,可为高侵彻威力EFP战斗部成型设计提供一个标准构型参考。展开更多
In this paper, a practical decoupling control scheme for fighter aircraft is proposed to achieve high angle of attack(AOA)tracking and super maneuver action by utilizing the thrust vector technology. Firstly, a six de...In this paper, a practical decoupling control scheme for fighter aircraft is proposed to achieve high angle of attack(AOA)tracking and super maneuver action by utilizing the thrust vector technology. Firstly, a six degree-of-freedom(DOF) nonlinear model with 12 variables is given. Due to low sufficiency of the aerodynamic actuators at high AOA, a thrust vector model with rotatable engine nozzles is derived. Secondly, the active disturbance rejection control(ADRC) is used to realize a three-channel decoupling control such that a strong coupling between different channels can be treated as total disturbance, which is estimated by the designed extended state observer. The control surface allocation is implemented by the traditional daisy chain method. Finally,the effectiveness of the presented control strategy is demonstrated by some numerical simulation results.展开更多
基金Projects(51808563,51925808)supported by the National Natural Science Foundation of ChinaProject(KLWRTBMC18-03)supported by the Open Research Fund of the Key Laboratory of Wind Resistance Technology of Bridges of ChinaProject(2017YFB1201204)supported by the National Key R&D Program of China。
文摘In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section.
文摘爆炸成型弹丸(explosively formed projectiles,EFP)的飞行稳定性直接决定弹丸撞靶的姿态、速度和密集度,进而影响EFP的侵彻性能。为了提升高超音速(Ma=4~7)EFP的侵彻威力,综述目前EFP的构型及飞行稳定性,建立了大长径比尾裙和褶皱尾翼EFP模型;构建并验证了EFP高超音速气动参数的数值计算方法。分析了尾翼式EFP的结构参数(齿根高、齿宽、实心率)对升阻力、压心和飞行稳定性等的影响规律,研究了结构不对称程度和滚转运动对尾裙和尾翼式EFP静态气动参数的影响规律。在此基础上,建立并验证了EFP飞行动力学微分方程,分析了结构非对称和滚转运动对弹道径向偏移量的影响;研究了药型罩材质对球形、尾裙式、尾翼式EFP长距离飞行速度降的影响,定量分析了飞行稳定性对EFP存速能力的影响。研究表明:常规尾翼弹飞行稳定性判据仍适用于EFP高超音速空气弹道;通过斜置褶皱尾翼产生较低速的滚转运动,可以显著提高非对称结构EFP的空气弹道密集度;优化后的尾翼式EFP在飞行稳定性良好的同时,具有优异的存速能力,可为高侵彻威力EFP战斗部成型设计提供一个标准构型参考。
基金supported by the National Natural Science Foundation of China(61973175,61973172)。
文摘In this paper, a practical decoupling control scheme for fighter aircraft is proposed to achieve high angle of attack(AOA)tracking and super maneuver action by utilizing the thrust vector technology. Firstly, a six degree-of-freedom(DOF) nonlinear model with 12 variables is given. Due to low sufficiency of the aerodynamic actuators at high AOA, a thrust vector model with rotatable engine nozzles is derived. Secondly, the active disturbance rejection control(ADRC) is used to realize a three-channel decoupling control such that a strong coupling between different channels can be treated as total disturbance, which is estimated by the designed extended state observer. The control surface allocation is implemented by the traditional daisy chain method. Finally,the effectiveness of the presented control strategy is demonstrated by some numerical simulation results.
