稀薄大气密度涨落对高空超高速飞行器气动性能的影响

地球周围的大气环境特性,随高度的上升,显著变化。对于本文关心的高度100km附近高超声速飞行器气动特性而言,稀薄大气密度涨落影响是一个重要的问题。按照大气层划分,高度100 km属于热层。热层的下界高度约86 km,上界高度与太阳活动有关,在太阳宁静期约为200 km,太阳活动期约500 km。热层下接中间层(高度50～86 km),上连电离层(高度80～1000 km),大气研究已知,中间层主要受重力波和湍流影响,电离层主要受太阳活动和地磁效应影响。高度100 km附近空域,处在热层下界,重力波、湍流、太阳活动和地磁效应等均有影响,理论上需要Navier-Stokes方程和Maxwell方程..

Separate modeling of trace species in hypersonic rarefied gas flows

Trace species in hypersonic rarefied gas flows play an important role in predicting electromagnetic phenomena.A typical example appeared in the RAM-C Ⅱ flight test:the mole fraction of trace species were several orders lower than those of primary species of the upcoming air flows,but dominated th..

高超声速稀薄电离气体电场效应的TSS计算

在TSS计算方法的基础上,考虑了空气分子转动和振动松弛速率与温度场的相互影响,模拟了美国电波衰减飞行试验(RAM C-II)过渡流区的电子密度分布,电场采用Langmuir and Tonks公式计算,比较了考虑电场与不考虑电场情况下对电子数密度分布的影响,同时跟美国电波衰减飞行试验(RAM C-Ⅱ)数据做了比较,所得结果与飞行测量数据相符甚好

中国科学院力学研究所高温气体动力学国家重点实验室;

再入过程中的电子数密度,在一定高度范围,随着再入高度的降低而增大。给定通讯频率,通讯中断的始发高度,是实际关心的问题。为了弄清通讯中断机理,美国在上世纪60年代,历时10年,开展一系列飞行试验[1,2],RAM C-II是其中的一次。根据文献[2]报道,RAM C-II试验测量得到的电子密度,随时间波动,最大值与最小值相差约3倍(图1)。这种差别被认为缘自飞行攻角的影响,因为在飞行过程中,飞行器有滚转,电子密度测量仪有时处于迎风面,有时处于背风面。虽然有许多研究者对RAM C-II的电子密度进行了计算,但几乎

Efficient computation of ultraviolet radiation from bow shock waves

Ultraviolet(UV)emissions radiated by nitric oxide(NO)and hydroxyl radical(OH)in the bow shock experiment[1]are computed using the direct simulation Monte Carlo(DSMC)method and the Navier–Stokes equations,respectively.Compared to previous studies[2,3],the trace species separation(TSS)algorithm[4]i..

Backscattering measurements of plasma coated target in high-enthalpy wind tunnel

利用JF10 高焓激波风洞设施, 进行了等离子鞘包覆目标的电磁散射测量实验. 基于矢量网络仪的步进扫频体制, 在C 波段进行实验, 观测到等离子鞘对目标雷达散射截面(radar cross section, RCS) 的影响. 并且,目标散射测量值中直接体现了激波风洞的高速气流状态信息: 气流前段会造成散射回波的剧烈变化且稳定性差, 持续0.5&mdash;1 ms; 激发的等离子鞘有效持续时间仅约为2 ms, 衰减了目标RCS 回波.</p

Monte Carlo modeling of electron density in hypersonic rarefied gas flows

The electron density distribution around a vehicle employed in the RAM-C II flight test is calculated with the DSMC method. To resolve the mole fraction of electrons which is several orders lower than those of the primary species in the free stream, an algorithm named as trace species&nbsp;separation&nbsp;(TSS) is utilized. The TSS algorithm solves the primary and trace species separately, which is similar to the DSMC overlay techniques; however it generates new simulated molecules of trace species, such as ions and electrons in each cell, basing on theionization&nbsp;and recombination rates directly, which differs from the DSMC overlay techniques based on probabilistic&nbsp;models.&nbsp;The electron density distributions computed by TSS agree well with the flight data measured in the RAM-C II test along a decent trajectory at three altitudes 81km, 76km, and 71km.</span

高空高速飞行器的紫外辐射特性

本文研究高度100 km附近高超飞行器的紫外辐射特性。分别考虑两种情况,外形均为半径10cm的圆球。第一种情况,来自美国弓形激波紫外辐射第二次飞行试验(BSUV),飞行速度约5.1 km/s,高度80～100km;第二种情况,来流速度7.5km/s,高度100～130km。在上述高度范围内,圆球周围流动是稀薄、非平衡的,故采用直接模拟Monte Carlo(DSMC)方法。计算程序是我们自己编制的(3R),可分析多组分、分子内能激发、化学反应、物面催化复合等,几何外形用表面元标示,可处理三维复杂外形,经过并行化,即使近连续介质区三维非平衡稀薄气流,也可在可承受时间内完成。本工作的难点在于紫外辐..

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies