激光对红外制导反舰导弹的干扰与损伤分析

计算了激光斜程传输时的大气透过率,研究了激光对光电探测器的干扰和破坏。以1.06μm激光辐照PV型HgCdTe红外探测器为例,估算了对远距离红外制导反舰导弹实现有效干扰所需发射的激光能量,从理论上证明了低能量激光对红外制导反舰导弹的干扰与损伤的可行性。     

固液混合火箭发动机喷焰红外辐射特性分析

为了研究固液混合火箭发动机喷焰在不同飞行状态的红外辐射特性,建立了固液两相状态下喷焰的红外辐射计算模型,获得了喷焰在2~12μm波段的红外辐射.将喷焰的温度、压力、摩尔组分等作为输入条件,米氏散射(Mie)模型计算颗粒相的散射,采用有限体积法(FVM)离散辐射传递方程,利用中分辨率大气辐射传输(MODTRAN)模型计算不同观测距离的大气透过率,编程计算得到不同飞行高度,不同观测方向下喷焰的红外辐射.结果表明喷焰红外辐射亮度与温度分布类似,在2.7~3.0μm和4.2~4.5μm波段范围内的辐射较强,高温粒子在近红外比远红外对总辐射的贡献大,太空与地面观测不同飞行高度的发动机喷焰辐射率因大气衰减的不同而有所差异,可为目标跟踪与发动机设计提供参考.      

聚焦脉冲激光大气传输热晕效应的数值分析

利用激光大气传输四维程序对序列脉冲激光大气传输热晕效应进行了数值计算和分析。对于均匀大气路径上聚焦传输序列脉冲激光进行数值仿真计算得到,风场渡越时间内的脉冲数Np在2~6之间有利于传输;然后对实际大气模式下序列脉冲激光进行了数值计算,得到的平均脉冲数-NP可以在一定条件下对序列脉冲激光进行定量表征的结论。     

红外辐射大气透过率的工程计算

针对现有红外辐射大气透过率经验计算公式不适用于高层大气的局限性,对其进行了重新推导并引入了高度修正,修正后的公式可用于计算任意高度路程上的大气透过率,修正所需大气光学特性参数全部可查相关手册获得。此外,还设计了适合于计算倾斜路径上大气透过率的计算流程,并给出了计算实例。     

大气信道对沿海激光通信的影响分析

为利于沿海靶场激光通信系统的设计与应用,研究分析了晴天、轻霾天、雾天、湍流等常见天气中大气信道对激光通信的影响。针对短距离近地面传输特点,利用经验数学模型仿真分析了激光透过率与能见度以及误码率与折射率结构常量的定量关系。结果表明：激光波长越长,衰减和湍流效应影响越小;晴天大气衰减对通信影响最小,轻霾天次之,雾衰减影响最严重;强湍流闪烁效应对误码率影响较大,但增加链路高度和选择长波长激光可减小影响。     

战斗机8~14μm波段红外特征及低发射率材料隐身效果

对某典型战斗机在8~14μm波段范围内的红外积分辐射强度空间分布进行了数值计算,考虑了大气透过率的影响,计算了使用红外搜索跟踪系统对战斗机进行探测时的探测距离,并分析了该战斗机采用低发射率材料后的红外隐身效果.战斗机的流场采用商用Fluent软件进行计算,红外辐射特征及探测距离采用自开发的NUAA-IRSE软件进行计算.计算结果表明:在8~14μm波段,周向角一定时,俯仰角越大红外积分辐射强度越大;俯仰角一定时,周向角越大红外积分辐射强度越大.采用低发射率材料后,战斗机在整个空间方向范围内,其红外积分辐射强度降低,战斗机红外隐身效果提高.      

航空发动机排气系统红外辐射特征数值计算研究

基于N—S方程,建立了某型发动机排气系统的数值计算模型;利用辐射传输方程（RTE）积分法所编制的红外辐射特征计算程序,计算了该发动机在地面工作状态下的红外辐射特征分布;在加力状态下,考虑了soot粒子的光谱吸收与发射。分析了水蒸气、二氧化碳、一氧化氮和一氧化碳气体介质的红外光谱吸收与发射,并考虑了红外辐射在大气中的传输,最后给出了在3.0～5．0μm波段内排气系统的红外辐射强度分布。     

激光推进发射微小卫星弹道仿真与分析

建立了初步的激光大气传输模型和光船的三维运动模型,通过对单站大气盘旋入轨模式下的推进弹道仿真分析可知,单站推进模式下激光在稠密大气层中行程较大,激光传输衰减严重。针对上述问题,以激光推进发射微小卫星为应用目标,提出了基于过顶接力和等光程接力两种方式下三站入轨的推进模式,给出并分析了相应的仿真结果,并利用等光程接力方式分析了激光推进发射微小卫星的运载能力。结果表明,三站等光程接力方式可以有效的解决激光传输问题,减小了激光在稠密大气层中的传输距离和激光的传输损失,提高入轨质量。     

基于地球红外背景模拟的 水云大气影响初步分析

为支持地球红外背景的模拟研究,以天基观测为前提,计算了2个大气窗口下,4个具有典型大气和地表特征的区域在水云大气下的路径透过率和各成分辐射亮度。通过相对变化比例,讨论了地球背景模拟中水云与地表的图像区分以及地域的影响。结果表明,水云对地球背景辐射传输影响显著:云层下方辐射会被强烈衰减,同时观测路径中的散射辐射大幅增强。在同一选定区域下,积云大气的观测路径亮度相对无云大气下变化最大,在相同水云类型条件下,大气散射和太阳散射亮度在不同区域区别较大,说明在模拟水云地球背景时不能忽略地域的影响。计算和分析结果可为地球背景模拟中的水云红外图像生成提供一定的数据基础和技术支持。     

火箭发动机羽流红外特性计算方法研究

为研究火箭发动机羽流近场的红外辐射特性,建立了羽流红外辐射传输的计算模型,通过在能量方程中引入辐射源项,实现了流场计算与辐射传输的耦合求解。计算中考虑了7种主要燃气组分,分别使用有限体积法和离散坐标法求解羽流流场和辐射传输方程,得到了羽流红外辐射强度在1～15μm范围内随波长变化的曲线及辐射强度在近场内的分布云图,均与文献的计算结果和红外试验热图符合较好。在羽流近场内能够捕捉到流场内各点辐射强度随流场物性变化的情况,表明耦合求解能提高辐射计算精度。     

Analysis of a Long-Distance System Measuring the Concentration of Atmospheric Gaseous Pollutants

A detailed inaccuracy and sensitivity analysis of a long-distance air pollution detection system, using a laser measuring the resonance absorption of polluting molecules, is introduced. The noise and the dynamic range of the radiation detectors used, the atmospheric inhomogeneities, and the atmospheric propagation losses of the electromagnetic radiation are considered. In addition, the best measuring path length as a function of a molecule density and atmospheric transparency and irregularity is discussed.     

脉冲激光辐射下VO_2薄膜的光限幅性能

采用反应溅射和后续退火工艺,在石英衬底上制备具有热致相变特性的VO_2薄膜,并对薄膜的光学性能进行表征。研究发现:在弱光辐射下,随着温度的改变,薄膜的透射率在可见及近红外光区会发生显著变化,具有良好的相变光开关特性;在强光辐射下,制备的VO_2薄膜同样具有良好的红外光调制深度;当脉冲激光波长为1064 nm时,随着脉冲能量的逐渐增强,薄膜的表面反射率逐渐降低,光限幅性能呈现出先升高再降低的趋势,其透射率最低可降至7%,薄膜的脉冲激光损伤阈值约为50 mJ/cm~2。     

Numerical simulation of the infrared radiative signatures of liquid and solid rocket plumes

In this paper, a finite volume method was developed to compute the infrared radiative signatures of both liquid and solid rocket plumes, and to investigate the radiative signatures on two wavebands, 2–6 and 8–12 μm bands, respectively. This method is based on the radiative transport equation for local thermodynamic equilibrium, which accounts for radiative heat transfer in inhomogeneous emitting, absorbing, and non-isotropic scattering media. The radiative properties of combustion gases are computed by using the Elsasser narrow band model, and that of particles are computed by using the Mie scattering theory. A numerical method is applied to solve the following three problems. The first one is the computation of the radiative heat transfer in an absorbing, emitting and isotropic scattering homogeneous cylindrical medium in which the radiative flux is presented. The other two are the computations of the infrared radiation of plumes from the liquid and solid rockets in which both the source and apparent radiant intensities are presented as results. The atmospheric absorption effect on the radiation of plumes is also considered by calculating the atmospheric transmittance using MODTRAN. Some of these results, compared with those available in the literature, have shown satisfactory agreement in most cases.     

Detection Statistics for Laser Radar in Atmospheric Turbulence with Fluctuating Targets

The probability of detection and false-alarm rates are developed for laser radar systems perturbed by background radiation, fluctuating targets, and atmospheric turbulence. In particular, some results on the decibel loss due to atmospheric turbulence are presented.     

A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave observations in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfvén waves and particle precipitation related to solar and magnetospheric processes. We review ionospheric processes as well as surface and space weather phenomena that drive the coupling between the troposphere and the ionosphere. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface perturbations and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and to solve inverse problems and outline in a final section a few challenging subjects that are important to advance our understanding of tropospheric-ionospheric coupling.     

均匀各向同性大气湍流对声爆传播特性的影响

基于离散Fourier模态有限和生成的随机大气湍流场，采用修正波形参数方法，开展了均匀各向同性大气湍流对典型超声速客机声爆传播特性的影响分析。计算采用的超声速客机模型为自行生成的简化超声速公务机模型。首先，应用航空工业空气动力研究院自主研制的CFD软件ARI_Overset在三维空间求解Navier-Stokes方程，得到作为声爆远场传播初始值的近场空间压力分布；其次，基于Von Karman能量谱，采用离散Fourier模态有限和形式生成随机均匀各向同性大气湍流场；最后，采用修正波形参数方法模拟了声爆信号在随机速度湍流场中的传播过程。数值结果表明：各向同性大气湍流对于地面声爆特征有重要影响。与无湍流状态相比，均匀各向同性大气湍流使得地面声爆特征增强的概率约为55%，使得地面声爆特征减弱的概率约为45%，故总体而言大气湍流效应更倾向于增强地面声爆特征；均匀各向同性大气湍流对于声爆传播路径影响相对较小，但是这一变化仍会导致地面信号接收点的不确定性。