目的研究航行体跨音速斜射入水的流动特性,获得不同入水攻角下航行体跨音速可压缩入水特性。方法建立跨音速航行体的几何模型,采用VOF(Volume of Fluid)均相流模型、SST k-ω湍流模型和Zwart空化模型进行数值模拟,并进行液相可压缩修正...目的研究航行体跨音速斜射入水的流动特性,获得不同入水攻角下航行体跨音速可压缩入水特性。方法建立跨音速航行体的几何模型,采用VOF(Volume of Fluid)均相流模型、SST k-ω湍流模型和Zwart空化模型进行数值模拟,并进行液相可压缩修正,对比不同入水攻角下的入水可压缩流动特性,分析绕航行体空泡的发展规律与航行体姿态和受力特性。结果计算了不同入水攻角下航行体跨音速斜射入水可压缩流动特性,入水攻角对空泡直径几乎没有影响,但不同攻角下,空泡形态随时间的发展明显不同,并且随着正负攻角的增加,空泡的完整性遭到破坏。航行体弹道轨迹偏移量,随正攻角的增大而增加,随负攻角的增大先增加、后减小。航行体水平和垂直受力随正攻角的增大而减小,随负攻角的增大先增大、后减小。结论在不同入水攻角下,航行体跨音速入水流动结构的发展具有相似性,但是随着攻角的变化,入水空泡结构、弹道偏移、受力特性都发生明显变化。展开更多
A new guidance scheme for the approach and landing (A & L) phase of an unpowered reusable launch vehicle (RLV) has been developed. The main advantage of the new guidance is the use of glide-efficiency factor as th...A new guidance scheme for the approach and landing (A & L) phase of an unpowered reusable launch vehicle (RLV) has been developed. The main advantage of the new guidance is the use of glide-efficiency factor as the independent variable to compute the geometrical flare parameters by a set of analytical functions. The trajectory-planning algorithm generates its reference geometry based on the steep and shallow subphases, respectively. During the steep segment, the quasi-equilibrium glide (QEG) solution, which assumes a constant dynamic pressure and flight-path angle during the flight, is used to create the flight reference while the shallow segment is defined by polynomial functions for altitude and dynamic pressure profiles. Standard linearization methods are used to design a closed-loop command in order to track the QEG profile. Furthermore, proportion-derivative (PD) control is used to modulate the lift coefficient during the flare flight. Once the reference trajectory is created, a closed-loop simulation is obtained to track the reference. Off-nominal conditions, in terms of change in initial glide-efficiency factor, dynamic pressure, flight-path angle, and altitude are tested using a Monte-Carlo simulation. The simulated results demonstrate the effectiveness of the proposed algorithm to land the vehicle successfully under large dispersions of glide-efficiency factor.展开更多
文摘目的研究航行体跨音速斜射入水的流动特性,获得不同入水攻角下航行体跨音速可压缩入水特性。方法建立跨音速航行体的几何模型,采用VOF(Volume of Fluid)均相流模型、SST k-ω湍流模型和Zwart空化模型进行数值模拟,并进行液相可压缩修正,对比不同入水攻角下的入水可压缩流动特性,分析绕航行体空泡的发展规律与航行体姿态和受力特性。结果计算了不同入水攻角下航行体跨音速斜射入水可压缩流动特性,入水攻角对空泡直径几乎没有影响,但不同攻角下,空泡形态随时间的发展明显不同,并且随着正负攻角的增加,空泡的完整性遭到破坏。航行体弹道轨迹偏移量,随正攻角的增大而增加,随负攻角的增大先增加、后减小。航行体水平和垂直受力随正攻角的增大而减小,随负攻角的增大先增大、后减小。结论在不同入水攻角下,航行体跨音速入水流动结构的发展具有相似性,但是随着攻角的变化,入水空泡结构、弹道偏移、受力特性都发生明显变化。
文摘A new guidance scheme for the approach and landing (A & L) phase of an unpowered reusable launch vehicle (RLV) has been developed. The main advantage of the new guidance is the use of glide-efficiency factor as the independent variable to compute the geometrical flare parameters by a set of analytical functions. The trajectory-planning algorithm generates its reference geometry based on the steep and shallow subphases, respectively. During the steep segment, the quasi-equilibrium glide (QEG) solution, which assumes a constant dynamic pressure and flight-path angle during the flight, is used to create the flight reference while the shallow segment is defined by polynomial functions for altitude and dynamic pressure profiles. Standard linearization methods are used to design a closed-loop command in order to track the QEG profile. Furthermore, proportion-derivative (PD) control is used to modulate the lift coefficient during the flare flight. Once the reference trajectory is created, a closed-loop simulation is obtained to track the reference. Off-nominal conditions, in terms of change in initial glide-efficiency factor, dynamic pressure, flight-path angle, and altitude are tested using a Monte-Carlo simulation. The simulated results demonstrate the effectiveness of the proposed algorithm to land the vehicle successfully under large dispersions of glide-efficiency factor.
