A sounding rocket experiment on the marangoni convection

During a 6-minutes free flight of a sounding rocket an experiment on the thermal Marangoni convection in a right circular cylindric floating zone was carried out to verify the thermal Marangoni convection by flow visualisation for the first time at 10^?4 g. From the motion picture analysis the velocity distributions are obtained. The interdependence between the two velocity maxima and the S-shaped temperature distribution on the free surface is discussed. The influence of the heat transfer caused by the flow of the surrounding air induced by the thermal Marangoni convection itself is considered briefly.     

Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.     

临近空间环境下封闭方腔内耦合换热特性

以临近空间浮空器载荷舱为应用背景,对复杂热边界条件下含热源的三维封闭方腔内自然对流、表面辐射和导热的耦合问题进行了数值模拟。综合考虑对流换热、长波辐射、太阳辐射等因素的影响,建立了临近空间热环境模型。通过Fluent软件用户自定义函数（UDF）引入外部非定常的辐射-对流耦合热边界条件,对腔内换热特性的昼夜变化进行研究,并分析了腔壁厚度、发射率和导热系数对其的影响。数值结果表明,腔内平均温度昼夜变化很小,约为12.9 K,但温度场分布随太阳方位变化而变化;腔内对流换热较弱,同一时刻最大温差约为71.3 K;腔壁热阻和发射率增加会削弱自然对流的强度。      

On the generation of the stimulated electromagnetic emission. The computer simulation results

Results of computer simulations of the broad continuum (BC) feature of stimulated electromagnetic emissions (SEE) of the ionosphere are presented. The simulations were performed using the model of BC generation based on the double transformation of electromagnetic waves to upper hybrid (UH) waves and back with artificial small scale irregularities (ASI) of plasma density. An induced scattering of the UH waves by thermal ions provided a wide spectrum of SEE. For the simulations an empirical model of the ASI spectrum, development and decay was used.     

相变储热/辐射器式热沉的传热特性研究

对一种用于舱外活动的相变储热/辐射器式热沉进行了实验研究和数值模拟.设计了相变储热器的实验件和实验方案,进行了储热器的冷却实验.建立了具有导热与对流换热耦合边界的相变储热器数学模型,模型中考虑了自然对流及空穴的影响.编制了相变储热器的性能分析计算程序.通过实验值与计算值的比较分析,验证了程序的可靠性.该模型及计算程序为相变储热器的设计和优化提供了有利的分析工具.     

航天器舱内气体对流换热的地面模拟试验方法

对航天器舱内气体对流换热的地面模拟试验方法进行了系统地理论分析,包括热缩比模型法、降压法和浓度比拟法三种。分别给出了各种方法的相似律或相似准则及其应用的约束条件,并从原理上定性比较这三种方法的优缺点。分析表明,热缩比模型法在保持Ｒｅｙｎｏｌｄｓ数不变的前提下可明显减弱自然对流的影响,但这种方法不能用于工程原型;降压法可用工程原型进行模拟试验,但不能用于液体流动问题;然而这两种方法的共同缺点是都不能完全消除自然对流;浓度比拟法理论上可以完全消除自然对流,但约束条件多,工程实现困难。     

A study of long-term climatology of ionospheric irregularities by using GPS phase fluctuations at the Brazilian longitudes

We have examined the ionospheric plasma irregularities that were recorded by using three ground-based receivers of the global positioning system (GPS) located at Brazilian longitudes during the period of a complete solar cycle, 1995–2005. The statistic results show that ionospheric irregularities are very easy to occur in December solstice months but rare to occur in June solstice months. Besides, the occurrence rates of irregularities in both December and June solstice months are little dependent on solar activity. However, in equinoctial months, the development of irregularities is obviously dependent on solar activity. There is a new finding in this study that if strong irregularities are distinguished from moderate ones, their occurrence rates would increase with solar activity during the December solstice months.     

夜侧极区电离层对流对行星际激波的响应

利用超级双子极光雷达网（Super Dual Aurora Radar Network,SuperDARN）高频雷达、北半球IMAGE地磁台链以及南极中山站的极光观测数据,研究电离层对流对2012年7月14日一个行星际激波扰动事件的响应.在18:10UT行星际激波到达地球并与磁层相互作用触发地磁急始和磁层亚暴,SuperDARN雷达观测到北半球夜侧极区电离层对流显著增强,观测视野覆盖黄河站的Hankasalmi雷达观测到从激波到达地球至18:33UT,电离层F层出现剧烈扰动,雷达回波数明显增多,并出现局部对流速度反转现象.18:33UT之后,观测到F层出现三块速度高达600m·s-1的逆阳运动不规则体.而与Hankasalmi雷达地磁共轭的南半球Kerguelen雷达探测到的回波主要来自E层,回波数量几乎无变化,但是Kerguelen雷达观测视野内的中山站全天空光学成像仪观测到极光活动显著增强.南北半球夜侧电离层观测结果的差异,主要是由于它们分别处于极夜和极昼.      

Enhancement of VLF-ducts under the action of high power radio wave on the ionospheric F-region

Wave effects are discussed pointing to improvement of whistler propagation in the ionosphere illuminated by a powerful radio wave. The large scale irregularities (ducts) responsible for these effects are formed in the illuminated ionospheric region by the process of electron heating by the fields of the pump wave and excited plasma oscillations. These irregularities may also be created in the ionosphere and plasmasphere by fluxes of suprathermal electrons accelerated by the plasma turbulence in the reflection region of the pump wave.     

准直光学系统热变形对太阳模拟器性能影响研究

为了给太阳模拟器系统热管理提供可靠的技术依据,研究了准直光学系统热变形对系统性能的影响。选取项目组自主研发的高精度太阳模拟器准直光学系统作为研究对象,利用有限元软件仿真实际工作条件下各光学元件表面温度及热变形分布,将通光表面变形数据拟合为泽尼克系数导入光学设计软件中,分析热变形对系统准直角误差及辐照均匀度影响。研究结果表明:在未采取温控措施的自然对流条件下,热变形造成±1’的准直角误差和41.3%的辐照不均匀度,超出允许范围,需进行温控。通过光机集成分析法,给出了不同温度下,对流系数与热变形导致的准直角误差和辐照不均匀度对应关系,为风冷温控系统工程化设计提供了依据。     

准直光学系统热变形对太阳模拟器性能影响研究

为了给太阳模拟器系统热管理提供可靠的技术依据，研究了准直光学系统热变形对系统性能的影响。选取项目组自主研发的高精度太阳模拟器准直光学系统作为研究对象，利用有限元软件仿真实际工作条件下各光学元件表面温度及热变形分布，将通光表面变形数据拟合为泽尼克系数导入光学设计软件中，分析热变形对系统准直角误差及辐照均匀度影响。研究结果表明：在未采取温控措施的自然对流条件下，热变形造成±1′的准直角误差和41.3%的辐照不均匀度，超出允许范围，需进行温控。通过光机集成分析法，给出了不同温度下，对流系数与热变形导致的准直角误差和辐照不均匀度对应关系，为风冷温控系统工程化设计提供了依据。     

实践十号卫星蒸发对流箱地面科学实验结果分析

实践十号卫星蒸发对流实验旨在研究置于加热底板的蒸发液滴在相变过程中,表面蒸发与表面张力驱动对流的耦合机理及其不稳定性.为与空间实验结果进行对比,利用蒸发对流箱完成在轨工况的科学匹配实验,获得相应工况的地面科学数据、工程参数及实验图像.通过对地面科学匹配实验结果进行分析,得到不同工况下液滴形貌（体积、表面积、接触角、液滴高度、液滴直径）变化规律,以及液滴蒸发过程中温度、热流量、蒸发速率和蒸发流量的变化规律.依据实验结果分析研究了具有质量交换的复杂流体相变界面的热质传输规律.      

长时间流星不均匀体母体特征个例研究

流星体坠入地球大气烧蚀电离产生流星等离子体尾迹,在等离子体不稳定性过程作用下产生流星不均匀体.利用光学视频和无线电雷达在低纬三亚开展流星体烧蚀和流星不均匀体综合探测结果,发展了一种获取流星不均匀体母体（流星体）特征参数的方法,并对2015年12月双子座流星雨期间观测的一次长持续时间流星不均匀体事例进行了分析,得到了其母体速度、质量和轨道等特征,结果显示产生这次流星不均匀体的流星体速度和轨道等具有双子座流星特点.该方法可应用于流星不均匀体及其母体特征研究.      

Study of mid-latitude ionospheric convection during quiet and disturbed periods using the SuperDARN Hokkaido radar

Westward ionospheric convective flows around midnight are frequently observed at mid-latitudes. They can be generated by so-called disturbance dynamo mechanisms working mainly in the mid-latitudes. To understand the influence of disturbance dynamo effects in the mid-latitudes, we studied the latitudinal distribution of westward flows in association with several kinds of geomagnetic disturbances using the SuperDARN Hokkaido radar. This radar creates high temporal resolution (1 s to 2 min), two-dimensional observations measuring the line-of-sight velocities of ionospheric plasma irregularities, which can be regarded as line-of-sight velocities of ionospheric convection in the mid-latitude region from 40° to 50°. This region could not be monitored using preexisting SuperDARN radars. In this study, we used ionospheric echo data obtained by the SuperDARN Hokkaido radar over 5 years (December 2006 to November 2011). We identified westward flows around midnight at about 40° to 55° geomagnetic latitude. Additionally, the data showed that the westward flow around midnight intensified under high geomagnetic activity (high Kp). This suggests that the disturbance dynamo could affect the mid-latitude ionospheric convection. We performed Superposed Epoch Analysis (SEA) to study the influences from the geomagnetic disturbances on mid-latitude ionospheric convection. We found no obvious influence during major storms (minimum Dst below −60 nT). SEA was also used to study the temporal and latitudinal dependence on the influences from substorms. From analysis of 36 events of AL-defined substorms, we saw that the influence of substorms lasted from 5 to 20 h after the onset between 44° and 53° geomagnetic latitude. The westward flow at mid-latitude grew to a maximum at 12 h after the geomagnetic substorm onset. This is consistent with the results of past numerical simulation studies of the disturbance dynamo effects.     

一种电离层场向不规则体各向异性散射模型

电离层场向不规则体散射具有很强的方向性, 利用电离层场向不规则体散 射进行VHF频段超视距通信时, 需要准确可靠地确定其散射分布特性及路径损 耗等参数. 基于电离层不规则体场向散射的特点, 以地球地磁场为坐标系统, 提出了一种电离层场向不规则体各向异性散射模型, 该模型能够计算前向和后 向散射链路的路径损耗分布、时延展宽和相干带宽等参数, 同时运用该模型对 雷达横向截面的计算结果与已有文献的数据结果进行对比, 证明了该模型的准确性. 该模型能够计算电离层场向不规则体VHF频段的散射分布及路径损耗等参数, 为VHF散射通信链路的设计、布站提供依据和技术指导.      

蒙皮热辐射特性对平流层浮空器氦气温度影响

分析了平流层球形超压浮空器在运行高度所受的各种环境辐射,研究浮空器处于热平衡状态时辐射传热、对流换热的作用规律,建立了浮空器的热平衡模型,分析太阳辐射、地面反照、地面辐射等环境辐照因素对浮空器全天各个时刻蒙皮材料和内部氦气平均温度影响,对比了吸收率、发射率和吸收发射比等辐射参数对浮空器热性能的影响.分析结果表明:具有低吸收发射比的蒙皮材料具有较好的热控效果;对于吸收发射比相同的蒙皮材料,具备低吸收率特性的蒙皮材料热控效果更为明显,更适用于长航时平流层超压浮空器.分析结果对浮空器蒙皮材料选择和总体设计具有指导意义.     

微重力环境下蒸发液层热毛细对流的数值模拟

提出了一种新模型来研究由单一物质构成的液层在其纯蒸气中的蒸发.液层置于微重力环境中并且受到水平方向温度梯度的作用,液层的热毛细对流和蒸发耦合在一起,使得气液界面的传热传质规律更加复杂.用理论分析的方法求解了不考虑热毛细效应的纯蒸发模型,得出温度场分布和界面质量流量的解析表达式.对于热毛细对流和蒸发耦合情况,采用有限差分的投影算法同时求解Navier-Stokes方程和能量方程,得到了不同蒸发Biot数和Marangoni数下流场和温度场的稳态数值解.论述了蒸发Biot数和Marangoni数对界面传热传质的影响,提出并解释了蒸发和热毛细对流耦合的三种模式.      

Plasma transport process in the equatorial/low-latitude ionosphere

The behaviour of the equatorial/low-latitude ionosphere and the transport processes during magnetic disturbed and quiet periods of a high solar activity year, 2014, in the American sector are investigated. Parameters used include vertical drift (Vz), transport term (W), NmF2, hmF2 and scale-height (H). The F2 plasma variations followed the diurnal local solar pattern, being higher at daytime. The sunset maximum and sunrise minimum peaks of hmF2 were directly opposite to the scale height (H) pattern. The plasma distribution was basically controlled by combined actions of the electrodynamic convection/thermospheric composition, which is geomagnetic activity dependent. The annual, semi-annual and winter-anomalies of the F2 parameters were higher at the dip equator in comparison with the low-latitude. The Vz pre-reversal peak magnitude coincided with hmF2 peak and the effects are more pronounced during geomagnetic disturbed conditions. The transport term pattern was similar to that of the scale height and it is suggested as a proxy parameter for quantifying low-latitude plasma irregularities and distribution of thermospheric composition.     

微重力条件下悬浮区中的Marangoni对流

本文研究微重力条件下悬浮区中的表面张力梯度驱动对流。采用有限元方法数值研究二维、轴对称悬浮区中的定常流动和温度分布,讨论P_r数及自由面上散热条件的影响。计算表明,P_r数(M_α数)增大时,流区大部分自由表面上温度梯度减小,流区流速较小,对流热输运较扩散效应增强。只要能维持自由面上一定的温度梯度,在较大的P_r数(M_α数)时,仍能得到收敛的定常解。     

层板内冷通道辐射换热影响

分析了层板换热过程,使用了"去除复杂表面"和"无限大平板" 等假设,给出了该假设下层板内腔辐射换热计算公式.又以一特定几何结构的层板模型为例,使用了3维流体力学计算程序求解了流-固耦合情况下的层板内部换热过程,研究了其在4种航空发动机典型工作状态下,内冷通道中的对流和辐射换热情况,得到了辐射与对流换热强度之比θ随冷气入口Re数和燃气加热功率的变化曲线,并对该曲线进行了指数拟合.建立了一套快速简捷计算层板内腔辐射状况的方法,为层板内腔换热研究是否应该忽略辐射,以及对层板冷却效果的修正,提供了一定的判断和计算依据.