In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as...In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as an example. In previous wind tunnel free-flight tests, the similarity law of vertical, downward, moving submunition was used to design submunitions at different positions in different initial-velocity directions, which resulted in large discrepancies between wind tunnel test results and real flight. In a wind tunnel test, each submunition has an independent time-reduction ratio with respect to the dispenser. Even if the separation trajectory of a single submunition is accurate, there will be errors in the position of each submunition at a given time. Therefore, it is necessary to determine the time-reduction ratio between submunitions, and to modify the test results later. In order to ensure the accuracy of wind tunnel test results, the similarity law of a freeflight test in a wind tunnel is derived in this paper. The time-correction scheme to ensure motion similarity between submunitions is solved. Numerical simulation is used to simulate the separation of a wind tunnel test and real aircraft, and the motion parameters of different submunitions are solved. The results show that the new similarity laws derived for different types of submunitions can greatly reduce the errors caused by previous similarity laws. In addition to the case for the separation of a cluster munition, the similarity law can also be applied to the free-flight test design of wind tunnels for vertical separation and horizontal separation of other kinds of aircraft.展开更多
Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-...Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests.The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages,as well as the influence of aerodynamic interference between the two stages on each other’s motion.From the perspective of multiangle physical equations,the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively,so as to ensure the authenticity and credibility of wind tunnel test results.The similarity law is verified by an HIFiRE-5 air vehicle,and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation.The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles.By analyzing the separation trajectory curve of the typical state,it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%,which indicates that this method is credible.The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.展开更多
The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in fr...The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in free-flying insects.This is particularly true at the intraspecific level,where variation in body mass and flight energetics may have direct consequences for the fitness of an individual.We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata.This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth.We show that the flight-MR scales with body mass to the power of 0.57,with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones.Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight,the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight.The metabolic cost of flight should therefore be studied under free-flight conditions,a requirement now enabled by the 13C technique described herein for insect flight.展开更多
By the study of extended range guided munitions (ERGM) trajectory characteristics, ERGM free-flight and glide trajectory characteristics are revealed and illustrated. On the basis of free-flight trajectory mathematica...By the study of extended range guided munitions (ERGM) trajectory characteristics, ERGM free-flight and glide trajectory characteristics are revealed and illustrated. On the basis of free-flight trajectory mathematical model, a two-parameter optimization problem of quadrant elevation and rocket ignition time is studied. Using the atmosphere mathematical model, the best glide-starting point of the downward trajectory is determined. With an optimal control mathematical model, the ERGM optimal glide trajectory is obtained.展开更多
基金supported by the Advanced Research Fund for Weapons and Equipment Development of China。
文摘In view of the separation form of the separator from the back of the carrier upward and from the side of the carrier outward, separation-safety research is carried out by taking the separation of a cluster munition as an example. In previous wind tunnel free-flight tests, the similarity law of vertical, downward, moving submunition was used to design submunitions at different positions in different initial-velocity directions, which resulted in large discrepancies between wind tunnel test results and real flight. In a wind tunnel test, each submunition has an independent time-reduction ratio with respect to the dispenser. Even if the separation trajectory of a single submunition is accurate, there will be errors in the position of each submunition at a given time. Therefore, it is necessary to determine the time-reduction ratio between submunitions, and to modify the test results later. In order to ensure the accuracy of wind tunnel test results, the similarity law of a freeflight test in a wind tunnel is derived in this paper. The time-correction scheme to ensure motion similarity between submunitions is solved. Numerical simulation is used to simulate the separation of a wind tunnel test and real aircraft, and the motion parameters of different submunitions are solved. The results show that the new similarity laws derived for different types of submunitions can greatly reduce the errors caused by previous similarity laws. In addition to the case for the separation of a cluster munition, the similarity law can also be applied to the free-flight test design of wind tunnels for vertical separation and horizontal separation of other kinds of aircraft.
基金supported by the National Natural Science Foundation of China(Nos.U21B2054 and 11772317).
文摘Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests.The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages,as well as the influence of aerodynamic interference between the two stages on each other’s motion.From the perspective of multiangle physical equations,the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively,so as to ensure the authenticity and credibility of wind tunnel test results.The similarity law is verified by an HIFiRE-5 air vehicle,and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation.The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles.By analyzing the separation trajectory curve of the typical state,it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%,which indicates that this method is credible.The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.
文摘The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level.However,methodological restrictions limit our understanding of the scaling of flight metabolic rate(MR)in free-flying insects.This is particularly true at the intraspecific level,where variation in body mass and flight energetics may have direct consequences for the fitness of an individual.We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata.This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth.We show that the flight-MR scales with body mass to the power of 0.57,with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones.Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight,the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight.The metabolic cost of flight should therefore be studied under free-flight conditions,a requirement now enabled by the 13C technique described herein for insect flight.
文摘By the study of extended range guided munitions (ERGM) trajectory characteristics, ERGM free-flight and glide trajectory characteristics are revealed and illustrated. On the basis of free-flight trajectory mathematical model, a two-parameter optimization problem of quadrant elevation and rocket ignition time is studied. Using the atmosphere mathematical model, the best glide-starting point of the downward trajectory is determined. With an optimal control mathematical model, the ERGM optimal glide trajectory is obtained.
