Near space has been paid more and more attentionin recent years due to its military application value.However,flow characteristics of some fundamental configurations(e.g.,the cavity)in near space have rarely been inve...Near space has been paid more and more attentionin recent years due to its military application value.However,flow characteristics of some fundamental configurations(e.g.,the cavity)in near space have rarely been investigated due to rarefied gas effects,which make the numerical simulation methods based on continuous flow hypothesis lose validity.In this work,the direct simulation Monte Carlo(DSMC),one of the most successful particle simulation methods in treating rarefied gas dynamics,is employed to explore flow characteristics of a hypersonic cavity with sweepback angle in near space by considering a variety of cases,such as the cavity at a wide range of altitudes 20-60 km,the cavity at freestream Mach numbers of 6-20,and the cavity with a sweepback angle of 30°-90°.By analyzing the simulation results,flow characteristics are obtained and meanwhile some interesting phenomena are also found.The primary recirculation region,which occupies the most area of the cavity,causes pressure and temperature stratification due to rotational motion of fluid inside it,whereas the pressure and temperature in the secondary recirculation region,which is a small vortex and locates at the lower left corner of the cavity,change slightly due to low-speed movement of fluid inside it.With the increase of altitude,both the primary and secondary recirculation regions contract greatly and it causes them to separate.A notable finding is that rotation direction of the secondary recirculation region would be reversed at a higher altitude.The overall effect of increasing the Mach number is that the velocity,pressure,and temperature within the cavity increase uniformly.The maximum pressure nearby the trailing edge of the cavity decreases rapidly as the sweepback angle increases,whereas the influence of sweepback angle on velocity distribution and maximum temperature within the cavity is slight.展开更多
Saucer-shaped aircraft adopts a novel aerodynamic configuration of blending fuselage with wing. In contrast to the ordinary aircraft configurations, this kind of configuration can totally eliminate the drag resulted f...Saucer-shaped aircraft adopts a novel aerodynamic configuration of blending fuselage with wing. In contrast to the ordinary aircraft configurations, this kind of configuration can totally eliminate the drag resulted from fuselage, bringing many advantages such as simple structure, compact scale, high load capability. But its small aspeet ratio makes the induced drag higher. Through wind tunnel experiments, it is discovered that a type of sweepback fin-shaped winglet can efficiently reduce the induced drag of this kind of aircraft. When this winglet is mounted to a model in wind tunnel experiment, the maximal ratio of lift to drag of the model can be increased by 75% as compared with the model without winglet at the speed of 30 m/s, and reached 15 at the speed of 50 m/s. In order to investigate the performance of this aircraft with winglet at low speed, test flights were processed. The results of test flights not only verify the conclusions of experiments in wind tunnel but also indicate that the load capability of the aircraft with winglet is increased and its lateral stability is even better than that of the aircraft without winglet.展开更多
The H-O grid is suggested to compute compressible flow past highly swept slender wing-body combinations. Full-potential equation, finite difference method and approximate factorization scheme are used. The computation...The H-O grid is suggested to compute compressible flow past highly swept slender wing-body combinations. Full-potential equation, finite difference method and approximate factorization scheme are used. The computations for the AGARD-B wing-body show that the code developed can apply to the cases from subsonic up to low supersonic free stream. The computed lift and pitching moment are in good agreement with the experimental results.展开更多
为了达到无需火箭辅助而增大射程,对国外采用弹体斜翼/尾翼的方式增加弹药射程的方案进行了介绍;该设计方案具有智能舵机控制,制导弹药从超音速、音速,到亚音速的整个滑行阶段,均将保持最大升阻比;为了分析超音速与音速滑行阶段内给定...为了达到无需火箭辅助而增大射程,对国外采用弹体斜翼/尾翼的方式增加弹药射程的方案进行了介绍;该设计方案具有智能舵机控制,制导弹药从超音速、音速,到亚音速的整个滑行阶段,均将保持最大升阻比;为了分析超音速与音速滑行阶段内给定的马赫数与攻角时不同斜翼的最佳后掠角状态,利用重叠网格法进行了系统的纳维-斯托克斯方程计算,通过对斜翼的最优配置设计,无需火箭助推便可使弹药达到100 n mile的目标射程。展开更多
A bionic gannet was developed based on the analysis of the body configuration and skeleton structure and the motion pattern of wings of a gannet in plunge-diving. In the current prototype, adjustable sweptback wings w...A bionic gannet was developed based on the analysis of the body configuration and skeleton structure and the motion pattern of wings of a gannet in plunge-diving. In the current prototype, adjustable sweptback wings were implemented so as to achieve different body shapes for entering water. The impact acceleration in the longitudinal body axis direction and the axial overload on the body were investigated through the falling-down experiments under different conditions including dropping height, water-entry inclination angle, and wing sweptback angle. It is found that when the above three key parameters are 10 m for dropping height, 0° for wing sweptback angle, and 90° for water-entry inclination angle, the maximum peak impact acceleration and overload are -167.20 m.s-2 and 18.06 respectively. Furthermore, the variation of peak impact acceleration with the three key parameters were also analyzed and discussed.展开更多
基金Project partly supported by the National Natural Science Foundation of China(Grant No.11802264)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180896)。
文摘Near space has been paid more and more attentionin recent years due to its military application value.However,flow characteristics of some fundamental configurations(e.g.,the cavity)in near space have rarely been investigated due to rarefied gas effects,which make the numerical simulation methods based on continuous flow hypothesis lose validity.In this work,the direct simulation Monte Carlo(DSMC),one of the most successful particle simulation methods in treating rarefied gas dynamics,is employed to explore flow characteristics of a hypersonic cavity with sweepback angle in near space by considering a variety of cases,such as the cavity at a wide range of altitudes 20-60 km,the cavity at freestream Mach numbers of 6-20,and the cavity with a sweepback angle of 30°-90°.By analyzing the simulation results,flow characteristics are obtained and meanwhile some interesting phenomena are also found.The primary recirculation region,which occupies the most area of the cavity,causes pressure and temperature stratification due to rotational motion of fluid inside it,whereas the pressure and temperature in the secondary recirculation region,which is a small vortex and locates at the lower left corner of the cavity,change slightly due to low-speed movement of fluid inside it.With the increase of altitude,both the primary and secondary recirculation regions contract greatly and it causes them to separate.A notable finding is that rotation direction of the secondary recirculation region would be reversed at a higher altitude.The overall effect of increasing the Mach number is that the velocity,pressure,and temperature within the cavity increase uniformly.The maximum pressure nearby the trailing edge of the cavity decreases rapidly as the sweepback angle increases,whereas the influence of sweepback angle on velocity distribution and maximum temperature within the cavity is slight.
文摘Saucer-shaped aircraft adopts a novel aerodynamic configuration of blending fuselage with wing. In contrast to the ordinary aircraft configurations, this kind of configuration can totally eliminate the drag resulted from fuselage, bringing many advantages such as simple structure, compact scale, high load capability. But its small aspeet ratio makes the induced drag higher. Through wind tunnel experiments, it is discovered that a type of sweepback fin-shaped winglet can efficiently reduce the induced drag of this kind of aircraft. When this winglet is mounted to a model in wind tunnel experiment, the maximal ratio of lift to drag of the model can be increased by 75% as compared with the model without winglet at the speed of 30 m/s, and reached 15 at the speed of 50 m/s. In order to investigate the performance of this aircraft with winglet at low speed, test flights were processed. The results of test flights not only verify the conclusions of experiments in wind tunnel but also indicate that the load capability of the aircraft with winglet is increased and its lateral stability is even better than that of the aircraft without winglet.
文摘The H-O grid is suggested to compute compressible flow past highly swept slender wing-body combinations. Full-potential equation, finite difference method and approximate factorization scheme are used. The computations for the AGARD-B wing-body show that the code developed can apply to the cases from subsonic up to low supersonic free stream. The computed lift and pitching moment are in good agreement with the experimental results.
文摘为了达到无需火箭辅助而增大射程,对国外采用弹体斜翼/尾翼的方式增加弹药射程的方案进行了介绍;该设计方案具有智能舵机控制,制导弹药从超音速、音速,到亚音速的整个滑行阶段,均将保持最大升阻比;为了分析超音速与音速滑行阶段内给定的马赫数与攻角时不同斜翼的最佳后掠角状态,利用重叠网格法进行了系统的纳维-斯托克斯方程计算,通过对斜翼的最优配置设计,无需火箭助推便可使弹药达到100 n mile的目标射程。
基金This work was supported by the National Natural Science Foundation of China （Grant no. 51005008）.
文摘A bionic gannet was developed based on the analysis of the body configuration and skeleton structure and the motion pattern of wings of a gannet in plunge-diving. In the current prototype, adjustable sweptback wings were implemented so as to achieve different body shapes for entering water. The impact acceleration in the longitudinal body axis direction and the axial overload on the body were investigated through the falling-down experiments under different conditions including dropping height, water-entry inclination angle, and wing sweptback angle. It is found that when the above three key parameters are 10 m for dropping height, 0° for wing sweptback angle, and 90° for water-entry inclination angle, the maximum peak impact acceleration and overload are -167.20 m.s-2 and 18.06 respectively. Furthermore, the variation of peak impact acceleration with the three key parameters were also analyzed and discussed.
