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81.
针对超临界流体物性的特殊性,对超临界喷射数值模拟方法进行研究。基于PR状态方程建立了考虑超临界流体特点的超临界喷射数值模型,并采用该模型对超临界C10H22喷射到超临界N2环境中的喷射进行了数值模拟。对比研究了采用PR状态方程的真实气体模型和理想气体模型得出的密度、温度、质量分数分布以及超临界喷射长度和喷射扩张角的变化规律和差异性,并与试验数据进行了对比。结果表明:2种模型在物性预测上的差异会造成以上喷射特性模拟结果的巨大差异,理想气体模型模拟结果与试验数据误差很大,利用真实气体模型能够得到与试验数据较为吻合的结果。基于PR状态方程的超临界喷射数值模型准确可靠,可为碳氢燃料的超临界喷射现象提供参考。 相似文献
82.
硬质聚氨酯具有刚度小、材质松散、易于吸收爆炸能量的特点,是一种很好的隔爆材料。为了设计环形切割器与后级随进战斗部之间的隔爆装置,利用LS-DYNA分别进行了圆柱型、圆锥型、球缺型3种聚氨酯隔爆体的数值模拟研究。通过研究得出结论:球缺型结构既节省材料,又可以更有效地降低前级产生的冲击波对后级战斗部的影响。该结论有助于带环形切割器串联战斗部的隔爆设计。 相似文献
83.
阐述了对我国首列200km/h动力分散型电动旅客列车组(先锋号列车)车体表面压力分布测试情况,对测量结果进行了较为详细的分析,最后用流场计算软件CFX对先锋号列车周围流场进行了数值模拟计算,并将计算结果与测量结果进行了对比,两者有较好的一致性。该研究结果可为空调装置及电器设备冷却风道进排风口位置的选取提供科学依据。 相似文献
84.
简述了大芯径大数值孔径光纤测试系统的测量原理,建立了测试系统的数学模型并对该系统的测量不确定度进行了评定。 相似文献
85.
Traditionally modeling for space science has concentrated on developing simulations for individual components of the solar
terrestrial system. In reality these regions are coupled together. This coupling can be as simple as the driving of the magnetosphere
– ionosphere – thermosphere system by the solar wind or as a complicated as the feedback of the ionospheric conductivity and
currents on the magnetosphere. As part of the CISM project we are beginning a concentrated effort to compressively model the
entire system. This approach includes chains of models. In the first chain physics based numerical models are utilized while
in the second chain empirical models are coupled together. The first half of this paper discusses the numerical modeling approach
by highlighting the coupling of pairs of regions within the system. In the second section we present results from empirical
models which are combined to make long term forecasts of conditions in the geospace environment. It is expected that a validated
and reliable forecast model for space weather can be obtained by combining the strongest elements of each chain. 相似文献
86.
We present grid-adaptive numerical simulations of magnetized plasma jets, modeled by means of the compressible magnetohydrodynamic
equations. The Adaptive Mesh Refinement strategy makes it possible to investigate long-term jet dynamics where both large-scale
and small-scale effects are at play. We extend recent findings for uniformly magnetized, periodic shear layers to planar and
fully 3D extended jet segments. The jet lengths cover multiple, typically 10, axial wavelengths of the fastest growing Kelvin–Helmholtz
(KH) like modes. The dominant linear MHD instabilities of the jet flows are quantified by means of MHD spectroscopic analysis.
In cases characterized by sonic Mach numbers about unity and large plasma beta values, both single and double shear layers
(planar jets) manifest self-organizing trends to large scales, e.g. by continuous pairing/merging between co-rotating vortices,
simultaneously with the introduction of small-scale features by magnetic reconnection events. The vortices form as a result
of KH unstable shear-flow layers, and their coalescence arises from the growth of subharmonic modes at multiple wavelengths
of the fastest growing KH instability. In extended two-dimensional jet segments, we investigate how varying jet width alters
this coalescence process occurring at both edges, e.g. by introducing Batchelor-like coupling between counter-rotating vortices
formed at opposing weakly magnetized, close shear layers. Finally, periodic segments of supersonic magnetized jets are simulated
in two- and three-dimensional cases, which are characterized by violent shock-dominated transients. 相似文献
87.
A Class of TVD Type Combined Numerical Scheme for MHD Equations With a Survey About Numerical Methods in Solar Wind Simulations 总被引:3,自引:0,他引:3
It has been believed that three-dimensional, numerical, magnetohydrodynamic (MHD) modelling must play a crucial role in a
seamless forecasting system. This system refers to space weather originating on the sun; propagation of disturbances through
the solar wind and interplanetary magnetic field (IMF), and thence, transmission into the magnetosphere, ionosphere, and thermosphere.
This role comes as no surprise to numerical modelers that participate in the numerical modelling of atmospheric environments
as well as the meteorological conditions at Earth. Space scientists have paid great attention to operational numerical space
weather prediction models. To this purpose practical progress has been made in the past years. Here first is reviewed the
progress of the numerical methods in solar wind modelling. Then, based on our discussion, a new numerical scheme of total
variation diminishing (TVD) type for magnetohydrodynamic equations in spherical coordinates is proposed by taking into account
convergence, stability and resolution. This new MHD model is established by solving the fluid equations of MHD system with
a modified Lax-Friedrichs scheme and the magnetic induction equations with MacCormack II scheme for the purpose of developing
a combined scheme of quick convergence as well as of TVD property. To verify the validation of the scheme, the propagation
of one-dimensional MHD fast and slow shock problem is discussed with the numerical results conforming to the existing results
obtained by the piece-wise parabolic method (PPM). Finally, some conclusions are made.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
88.
José Luis Ballester 《Space Science Reviews》2005,121(1-4):105-113
Prominence seismology is a rapidly developing topic which seeks to infer the internal structure and properties of solar prominences
from the study of its oscillations. An extensive observational background about oscillations in quiescent solar prominences
has been gathered during the last 70 years. These observations point out the existence of two different types of oscillations:
Flare-induced oscillations (winking filaments) which affect the whole prominence and are of large amplitude and small amplitude
oscillations which seem to be of local nature. From the theoretical point of view, few models have been set up to explain
the phenomenon of winking filaments while, on the contrary, for small amplitude oscillations a large number of models trying
to explain the observed features have been proposed. 相似文献
89.
90.
CAM后置处理研究 总被引:1,自引:0,他引:1
唐立山 《航空精密制造技术》2006,42(3):60-62
分析了数控加工后置处理技术的特征、面临的问题和当前的发展趋势,介绍了应用通用后置处理器开发定制专用后置处理器的实践。 相似文献