高速直升机旋翼/螺旋桨/机身干扰特性分析

研究双拉力螺旋桨复合式高速直升机的气动特性可以为高速直升机的设计及气动优化提供参考。基 于动量源方法构建针对双拉力螺旋桨复合式高速直升机旋翼/螺旋桨/机身干扰特性数值计算及分析方法;对 孤立旋翼、旋翼/机身干扰进行算例验证;应用所构建的方法对双拉力螺旋桨高速复合式直升机悬停及前飞状 态的干扰流场进行数值模拟,分析机身对悬停流场影响及不同前飞速度旋翼/螺旋桨/机身干扰特性。结果表 明:悬停时机身对气流的阻塞作用降低了旋翼的升力,螺旋桨对旋翼下洗气流的加速作用使旋翼升力提高;低 速前飞时旋翼/螺旋桨/机身干扰较大,主要体现在旋翼下洗流造成螺旋桨滑流偏折以及机翼上表面压力分布 增大,高速前飞时这种干扰较小。     

Superthermal electron’s effects on lump solitons structures in magnetized auroral plasma

Based on the considerations of the acknowledgements of the numerous space observations by satellites in the auroral plasma, astrophysics plasmas, spacecraft observations, various plasma models have been framed and revealed different interesting features, like electrostatic structures, solitary waves, double layers, supersolitons, etc. Soliton theory is a very efficient and competent way to describe nonlinear features. Using Viking satellite data in the auroral plasma, we have derived lump soliton solutions of the Kadomstev-Petviashvili (KP) equation by employing Hirota bilinear method. Due to its wide range of applications, the study of lump soliton is very attractive and important too. It has been shown that the lump solitons structures as well as in the one-dimensional form of lump soliton are varied with associated parameters in the auroral magnetized plasma. During the analysis of the features of the lump solitons, it is found that the system parameters play a pivotal role on the lump solitons structures.     

含源流场流动相似参数推导及其物理意义

现有的相似参数能够较好地解决无源流动的动力学相似和热力学相似问题。然而,如果流场中存在质量、动量和能量等源项,则须引入新的相似参数来指导实验的设计。首先,在连续介质假设、斯托克斯流体假设、量热完全气体假设和单相流假设的前提下,推导出了41个相似参数;然后,将之归纳整理成9个独立的相似参数,其中,3个与源项有关;最后,讨论了它们各自的物理意义。现有的单相流相似参数均可通过9个相似参数组合而来。实际应用中,可根据具体流动情况选择这9个相似参数中的某几个进行模拟。     

Mini-magnetosphere: Laboratory experiment,physical model and Hall MHD simulation

Magnetosphere with a size comparable to the ion kinetic scales is investigated by means of laboratory experiment, analytical analysis and Hall MHD simulation. In experiment a specific magnetic field was observed which is non-coplanar to dipole field, does not change sign at dipole moment inversion and could be generated only via the quadratic Hall term. Magnetopause position and plasma stand off distance were found to be profoundly different between the experimental regimes with small and large ion inertia length. In the previous studies of a mini-magnetosphere by kinetic codes such novel features were observed as absence of the bow shock and plasma stopping at the Stoermer particle limit instead of the pressure balance distance. Proposed analytical model explains these features by Hall currents which tend to cancel magnetic field convection by ions. Performed numerical simulation shows a good agreement with experiment and analytical model. It gives detailed spatial structure of the Hall field and reveals that while ions penetrate deep inside mini-magnetosphere electrons overflow around it along magnetopause boundary.     

Propagation of cylindrical and spherical dust–ion acoustic solitary waves in a relativistic dusty plasma

The properties of cylindrical and spherical dust–ion acoustic solitary waves (DIASW) in an unmagnetized dusty plasma comprising of relativistic ions, Boltzmann electrons, and stationary dusty particles are investigated. Under a suitable coordinate transformation, the cylindrical KdV equation can be solved analytically. The change of the DIASW structure due to the effect of geometry, relativistic streaming factor, ion density and electron temperature is studied by numerical calculation of the cylindrical/spherical Kdv equation. It is noted that with ion pressure the effect of relativistic streaming factor to solitary waves structure is different. Without ion pressure, as the relativistic streaming factor decreases, the amplitude of the solitary wave decreases. However, when the ion pressure is taken into account, the amplitude decreases as the relativistic streaming factor increases and is highly sensitive to relativistic streaming factor. Our results may have relevance in the understanding of astrophysical plasmas.     

飞机舱内噪声的研究现状

飞机舱内噪声是影响乘客舒适性的一项重要指标,舱内噪声的最小化是国内外共同追求的目标。在对飞机外部噪声源特性进行介绍的基础上,对噪声源/传递路径识别、舱内降噪措施以及声学试验计算等方面进行了综述。其中,噪声源以及噪声传递路径识别主要从各种识别技术手段方面展开了讨论,包括频率分析法、相关技术、修改噪声传递路径、空气传声以及结构传声的识别。而舱内降噪方法主要从被动降噪与主动降噪两方面进行全面介绍,指出被动降噪是一种修改与优化噪声传递路径的方法,而主动降噪能自动感应识别并控制噪声源,并分别给出了两者的优点及其局限性。在噪声测试与仿真模拟方面则介绍了国内外地面实验室舱内噪声的研究情况,并指出了国内的不足,对仿真计算理论进行了梳理,列出各自的适用范围。最后,指出了目前舱内噪声研究依然存在的问题与挑战,并给出了未来的研究方向。     

星敏感器杂散光抑制方法及仿真分析

星敏感器的探测目标是深黑空间中的恒星,属于暗目标探测系统,对杂散光的干扰非常敏感,因此,星敏感器杂散光抑制能力是其观测能力的重要影响因素。以点源透过率（PST）为评价指标,计算观测目标7.5等星时星敏感器需要达到的杂散光抑制指标,并以此为基础,提出一种有效的杂散光抑制方法,包括外遮光罩设计、消杂散光光阑设计,以及内部机械结构的关键表面的消杂散光处理。采用Lighttools软件对设计结果进行仿真,设计与分析结果表明,该杂散光抑制方法能够有效抑制星敏感器的杂散光,实现观测7.5等星的目标。      

涡轮导叶前缘多排孔冷气掺混数值模拟

针对某三维扭转冷却涡轮导叶在前缘开设3排冷却孔,冷却孔流向夹角均为90°,径向射流角分别为30°,60°和90°,分别采用点源项与真实孔射流两种方法对前缘冷却孔气动性能和冷却特性进行了对比研究,分析了点源项与真实孔冷气掺混机制以及不同径向射流角对叶栅通道流场和冷却特性的影响.结果表明:真实冷却孔射流对前缘附近约10%轴向弦长范围内的流动影响较大,冷却效果涵盖了整个导叶;点源项方法所得压力与非冷却涡轮很接近;冷气径向喷射角减小,真实孔模型导叶表面温度下降了8%~16%,而点源项模型导叶表面温度降低了21%~23%.在工程实际中不能将点源项法计算结果用作定量评估依据.      

太阳风中磁场重联离子扩散区的大尺度特征

利用ACE和WIND卫星2007年1月6日的联合探测, 在1AU附近发现了一个等离子体密度极低的Petschek-like重联喷流区. 该喷流区内部出现了非常明显的Hall双极磁场、等离子体密度下降区以及与Hall电流相符的低能段电子投掷角分布. 这些特征与重联离子扩散区的Hall效应非常吻合, 说明很可能在太阳风中观测到了一个离子扩散区. 分析表明, 与之相关的磁场重联为准稳态快速完全反向重联, 其扩散区以一对慢模波为边界, 空间尺度达到80个离子惯性长度, 表现出了大尺度重联的特征.      

Hybrid simulations of the O ion escape from Venus: Influence of the solar wind density and the IMF x component

As an initial effort to study the evolution of the Venus atmosphere, the influence of the solar wind density and the interplanetary magnetic field (IMF) x component (the x-axis points from Venus towards the Sun) on the O⁺ ion escape rate from Venus is investigated using a three-dimensional quasi-neutral hybrid (HYB-Venus) model. The HYB-Venus model is first applied to a case of the high-density (100 cm⁻³) solar wind interaction with Venus selected from the Pioneer Venus Orbiter observations to demonstrate its capability for the study. Two sets of simulations with a wide range of solar wind densities and different IMF x components are then performed. It is found that the O⁺ ion escape rate increases with increasing solar wind density. The O⁺ ion escape rate saturates when the solar wind density becomes high (above 100 cm⁻³). The results also suggest that the IMF x component enhances the O⁺ ion escape rate, given a fixed IMF component perpendicular to the x-axis. Finally, the results imply a higher ion loss rate for early-Venus, when solar conditions were dramatically different.