Numerical investigation on cavity structure of solid-fuel scramjet combustor

The influences of miscellaneous combustor structures for solid fuel scramjet combustion on the performance are investigated, including a detailed interaction analysis between shocks/waves and combustion. Hydroxyl-terminated polybutadiene is chosen as the solid fuel with the non-premixed equilibrium probability density function combustion model. The results show combustion enhancement when structure of combustor is modified. The radical emphasis is to examine the sensitivity of the properties due to variations on the length-to-depth ratio of cavity, aft wall angle, and offset ratio. It is noted that there is an appropriate structure of cavity (L/D=4, θ=45°, and D_d/D_u=1.25–1.5) regarding the combustion efficiency, total pressure loss and specific impulse. The observation of function for combustor components provides instructional insight into the design considerations for a combustor of a solid-fuel scramjet.     

Energization of Plasma Species by Intermittent Kinetic Alfvén Waves

We propose a new phase-mixing sweep model of coronal heating and solar wind acceleration based on dissipative properties of kinetic Alfvén waves (KAWs). The energy reservoir is provided by the intermittent ∼1 Hz MHD Alfvén waves excited at the coronal base by magnetic restructuring. These waves propagate upward along open magnetic field lines, phase-mix, and gradually develop short wavelengths across the magnetic field. Eventually, at 1.5–4 solar radii they are transformed into KAWs. We analyze several basic mechanisms for anisotropic energization of plasma species by KAWs and find them compatible with observations. In particular, UVCS (onboard SOHO) observations of intense cross-field ion energization at 1.5–4 solar radii can be naturally explained by non-adiabatic ion acceleration in the vicinity of demagnetizing KAW phases. The ion cyclotron motion is destroyed there by electric and magnetic fields of KAWs.     

Study of waves in the magnetotail region with cluster and DSP

The study of the neutral sheet is of fundamental importance in understanding the dynamics of the Earth’s magnetosphere. From the earliest observation of the magnetotail, it has been found that the neutral sheet frequently appears to be in motion due to changing solar wind conditions and geomagnetic activity. Multiple crossings of the neutral sheet by spacecraft have been attributed to a flapping motion of the neutral sheet in the north–south direction, a wavy profile either along the magnetotail or the dawn–dusk direction. Cluster observations have revealed that the flapping motions of the Earth’s magnetotail are of internal origin and that kink-like waves are emitted from the central part of the tail and propagate toward the tail flanks. This flapping motion is shown here to propagate at an angle of ∼45° with x_GSM. A possible assumption that the flapping could be created by a wake travelling away from a fast flow in the current sheet is rejected. Other waves in the magnetotail are found in the ULF range. One conjunction event between Cluster and DoubleStar TC1 is presented where all spacecraft show ULF wave activity at a period of approximately 5 min during fast Earthward flow. These waves are shown to be Kelvin–Helmholtz waves on the boundaries of the flow channel. Calculations show that the conversion of flow energy into magnetic energy through the Kelvin–Helmholtz instability can contribute to a significant part of flow breaking between Cluster and DoubleStar TC1.     

Shocks: Commonalities in Solar-Terrestrial Chains

Shocks are found throughout the heliosphere, wherever supersonic (or super-magnetosonic) flows encounter obstacles or other, slowly moving, media. Although some of the physical parameters are in different regimes, all shocks heat and decelerate the media incident upon them. Most shocks must propagate in a collisionless plasma, thereby adding importance to the particle interactions with the electromagnetic fields, and enabling some particles to be accelerated to high energies. This paper explores the commonalities, and differences, in shocks throughout the heliosphere, and concentrates on the role of shock microstructure in effecting the shock transition and in governing the resulting energy partition amongst the constituent species. Shocks play a significant role in the solar-terrestrial chain.     

Plasma Waves in the Hermean Magnetosphere

The Hermean magnetosphere is likely to contain a number of wave phenomena. We briefly review what little is known so far about fields and waves around Mercury. We further discuss a number of possible phenomena, including ULF pulsations, acceleration-related radiation, bow shock waves, bremsstrahlung (or braking radiation), and synchrotron radiation. Finally, some predictions are made as to the likelihood that some of these types of wave emission exist.     

ANALYSIS OF THE RETURNED SIGNAL MODEL IN BISTATIC RADAR SYSTEMS

ＡＮＡＬＹＳＩＳＯＦＴＨＥＲＥＴＵＲＮＥＤＳＩＧＮＡＬＭＯＤＥＬＩＮＢＩＳＴＡＴＩＣＲＡＤＡＲＳＹＳＴＥＭＳＹｉｎＣｈｅｎｇｙｏｕ，ＸｕＳｈａｎｊｉａ，ＷａｎｇＤｏｎｇｊｉｎ，ＺｈｏｕＬｉｎｙｕｎ（ＤｅｐａｒｔｍｅｎｔｏｆＥｌｅｃｔｒｏｎｉｃＥｎｇｉ...     

COMPUTING REACTIVE FLOW ON A COARSE GRID

INTRODUCTIONConsider the Euler equations supplementedby an additional reactive equation which consistsof a scalar balance law for the mass fraction ofunburntgasρρuρEρY t+ρuρu2 + pρu E + upρu Y x=κ000-ρΘ( T) Ywhereρ is the density,ρu the momentum,ρEthe total specific energy,ρY the mass fraction ofunburnt gas( 0≤ Y≤ 1 ) ,κ a large number( thereaction rate) and T temperature.Θ( T) =01 　if T≤ Tignif T>Tign,Tign is the ignition temperature,E=pγ- 1 + u22 + q0 Y,p is …     

非正弦波大电流短辐射器设计研究

赫兹电偶极子是一种辐射非正弦波的短辐射器,对赫兹电偶极子而言,必须施加很高的驱动电压,才能得到较大的天线电流,从而导致其辐射功率往往很小.研究设计了一种大电流短辐射器,它具有馈电容易,结构简单且对称等优点,从而可以简化理论分析并便于工程应用.     

准平行无碰撞激波的混合模拟

本文应用一维混合模拟方法数值研究了准平行无碰撞激波的结构.结果表明,激波上游的质子和准平行无碰撞激波相互作用后,有部分质子被激波反射,并向激波上游运动很长一段距离,从而激发起束流不稳定性,引起大振幅的共振右旋偏振的低频波动.这些波动在太阳风的带动下向激波下游运动,靠近激波后与激波合井,同时在激波的上游不断有新的波动产生.此过程能不断重复地进行.在平行无碰撞激波的情况下,在激波的下游还有大振幅的非共振右旋偏振的低频波动.激波上游的低频波动在向下游运动的过程中强度不断加强,最后超过原来激波的强度,形成新的激波.      

有涂覆层的导体圆柱空间散射特性的数值计算

文中根据带有涂覆层的导体圆柱在平面波的照射下的散射场表达式,进行了全面的数值计算,说明了虚宗量的Bessel函数和Hankel函数的计算方法,分别给出了平行极化波和垂直极化波入射时双站RCS的计算曲线,包括不同涂覆层厚度的影响、入射波频率、涂覆层介质的相对介电常数、导磁率变化时双站RCS的变化规律,获得了有参考意义的结果.