基于微型涡喷发动机热喷流的无源流体推力矢量喷管的控制规律

流体推力矢量喷管型面固定、活动部件少、结构重量轻，能够为高机动飞行器提供有效的飞行控制手段，但无源流体推力矢量喷管热喷流的偏转控制规律尚未完全掌握。为了推进无源流体推力矢量技术的实用化，本文设计研制了适用于微型涡喷发动机的耐高温喷管模型，对该喷管在微型涡喷发动机热喷流状态下的控制规律进行研究。利用非接触光学显示和测量手段——红外热成像拍摄和粒子图像测速（PIV）技术对主射流流动特性进行研究，获得流动矢量角随二次流控制阀门闭合度变化的控制规律；利用六分量盒式天平测力实验研究无源流体推力矢量喷管的力学特性，获得推力矢量角随二次流控制阀门闭合度变化的控制规律。研究结果表明：该构型喷管在微型涡喷发动机热喷流下主射流连续可控偏转，最大流动矢量角为-12.3°/12.3°，最大推力矢量角为-12.9°/12.8°，控制规律接近线性，不存在主射流偏转突跳问题。     

Abnormal changes of dynamic derivatives at low reduced frequencies

A number of studies have found that abnormal changes of dynamic derivatives occurred at very low reduced frequencies, but its inducement mechanism is not very clear. This paper has researched the abnormal changes and analyzed the influence on some parameters by solving the unsteady flow around forced oscillation airfoils based on Navier-Stokes equations. Results indicate that when the reduced frequency approaches to zero, the dynamic derivatives obtained by the numerical method will diverge. We have also proven it in theory that this phenomenon is not physical but completely caused by numerical singularity. Furthermore, the abnormal phenomenon can be effectively mitigated by using the time spectral method to solve the aerodynamic forces and the integral method to obtain the dynamic derivatives. When the reduced frequency is in the range of 0.001–0.01, the dynamic derivative maintains nearly unchanged for the whole speed region. This study can provide a reference for the reasonable choice of the reduced frequency in calculations and experiments of dynamic derivatives.     

Air route network optimization in fragmented airspace based on cellular automata

Air route network optimization,one of the essential parts of the airspace planning,is an effective way to optimize airspace resources,increase airspace capacity,and alleviate air traffic con gestion.However,little has been done on the optimization of air route network in the fragmented airspace caused by prohibited,restricted,and dangerous areas (PRDs).In this paper,an air route network optimization model is developed with the total operational cost as the objective function while airspace restriction,air route network capacity,and non-straight-line factors (NSLF) are taken as major constraints.A square grid cellular space,Moore neighbors,a fixed boundary,together with a set of rules for solving the route network optimization model are designed based on cellular automata.The empirical traffic of airports with the largest traffic volume in each of the 9 flight information regions in mainland China is collected as the origin-destination (OD) air port pair demands.Based on traffic patterns,the model generates 35 air routes which successfully avoids 144 PRDs.Compared with the current air route network structure,the number of nodes decreases by 41.67％,while the total length of flight segments and air routes drop by 32.03％ and 5.82％ respectively.The NSLF decreases by 5.82％ with changes in the total length of the air route network.More importantly,the total operational cost of the whole network decreases by 6.22％.The computational results show the potential benefits of the model and the advantage of the algorithm.Optimization of air route network can significantly reduce operational cost while ensuring operation safety.     

Alfvén gravity waves in viscous solar plasma: Effect of the background flow

We study the Propagation and damping properties of Alfvén gravity waves in the presence of the vertical magnetic field in the viscous solar plasma under influence of the background flow by deriving a fourth order dispersion relation in terms of the Doppler shifted frequency. We derive the dispersion relation under WKB and Boussinesq approximation. We study the damping of Alfvén gravity waves for the wave frequencies less than and greater than the Brunt-Väisälä frequency. We find that the Brunt-Väisälä frequency divides the frequency ranges where the weakly or strongly damped oscillations occur. The background flow exhibits a strong effect on weakly damped oscillations and a weak effect on the strongly damped oscillations. We also notice that the damping of both the strong and weakly damped oscillations depend on the Brunt-Väisälä frequency and wave number. The effect of the background flow is also being governed by the Brunt-Väisälä frequency and wave number. We also study the properties of gravity wave mode after filtering the Alfvén wave mode by minimizing the magnetic field and noticed that the background flow shows a very strong effect on the gravity wave mode.     

A data-driven approach to modeling high-density terminal areas: A scenario analysis of the new Beijing,China airspace

Airports are being developed and expanded rapidly in China to accommodate and pro-mote a growing aviation market. The future Beijing Daxing International Airport (DAX) will serve as the central airport of the JingJinJi megaregion, knitting the Beijing, Tianjin, and Hebei regions together. DAX will be a busy airport from its inception, relieving congestion and accommodating growth from Beijing Capital International Airport (PEK), currently the second busiest airport in the world in passengers moved. We aim to model terminal airspace designs and possible conflicts in the future Beijing Multi-Airport System (MAS). We investigate standard arrival procedures and mathematically model current and future arrival trajectories into PEK and DAX by collecting large quantities of publicly available track data from historical arrivals operating within the Beijing terminal airspace. We find that (1) trajectory models constructed from real data capture aberrations and deviations from standard arrival procedures, validating the need to incorporate data on histor-ical trajectories with standard procedures when evaluating the airspace and (2) given all existing constraints, DAX may be restricted to using north and east arrival flows, constraining the capacity required to handle the increases in air traffic demand to Beijing. The results indicate that the termi-nal airspace above Beijing, and the future JingJinJi region, requires careful consideration if the full capacity benefits of the two major airports are to be realized.     

涡轮流量计前导流件有限元计算分析

对涡轮流量计关键部件之一前导流件运用NX THERMAL/FLOW进行有限元计算分析,得出流量分离导致的大涡旋尾迹区易出现在前导流件尾部区域、前导流件叶片形状对此处流体速度变化具有较大影响的结论,为涡轮流量计和前导流件的设计提供了理论依据。     

先进航发旋转雾化喷嘴制造技术

喷射油道是一种高精度旋转雾化喷嘴,其非连续窄深端槽、窄深槽、3/4圆弧窄端槽为行业内少见结构.通过分析喷射油道特有结构的加工工艺,摸索油孔尺寸与燃油流量的匹配关系,解决了非连续深窄端槽、窄深槽、细微孔电火花成形加工、3/4圆弧窄端槽高效数控加工、高精度喷嘴孔流量调试等关键技术瓶颈,具有一定的指导意义和广阔的应用前景.     

Laminar flow control research at TsAGI: Past and present

This paper presents a brief review of activities in laminar flow control being performed at the Central Aerohydrodynamic Institute named after Prof. N.E. Zhukovsky (TsAGI). These efforts are focused on the improvement of the existing laminar flow control methods and on the development of new ones. The investigations have demonstrated the effectiveness of aircraft surface laminarization applications with the aim of friction drag reduction. The opportunity of considerable delaying of laminar-turbulent transition due to special wing profile geometry and using boundary layer suction and surface cooling has been verified at sub- and supersonic speeds through various wind tunnel testing at TsAGI and during flying laboratory experiments at the Flight Research Institute (LII). The investigations on using hybrid laminar flow control systems for friction drag reduction were also carried out. New techniques of laminar flow control were proposed, in particular, the method of local heating of the wing leading edge, boundary layer laminarization by means of receptivity control, and electrohydrodynamic methods of boundary layer stability control.     

带自由表面水流的分离涡模拟

目前水动力学问题的数值求解仍然广泛采用RANS模型,特别对于大尺度的地表水流的数值模拟,该类模型计算效率较高,但其难以给出湍流场的小尺度涡结构.深入研究复杂地形条件下的水流运动,需要发展诸如LES等的高级数值模型.天然地表水流,地形、边界复杂,雷诺数通常较高,高级数值模拟受限于计算能力的限制,还难以工程应用.RANS和LES混合模型是目前具有工程应用的一种混合数值模型,其已经在CFD领域获得了长足发展.然而对于地表水流运动的数值模拟,相关工作还较少.本文将分离涡模型(DES),即一种RANS和LES的混合模型,应用于带自由表面的地表水流运动,建立了一套数值仿真模型.模型基于有限体积法,水平面内采用非结构计算网格,垂向为结构化网格,对流项离散格式采用二阶TVD格式,并行基于OpenMP语言库.算例表明DES模型有助于揭示复杂地形条件下带自由表面水流的大涡拟序结构.     

基于非结构网格的不可压N-S方程多矩有限体积法

提出了一种基于三角形及四面体非结构网格的有限体积法(FVM),用以鲁棒且精确地求解不可压粘性流动问题.与传统的FVM方法仅将体积分平均值(VIA)作为计算变量的做法不同,本文提出的方法将VIA及点值(PV)同时作为计算变量并在每个迭代步进行计算更新.VIA以通量形式进行计算以确保数值守恒,PV可以通过控制方程的不同形式进行求解更新,无需守恒,因此可以采用非常高效的方法进行求解.将PV作为增加的变量使得紧致网格模板得以实现更高阶精度的重构,而且由此获得的数值模型对于非结构网格变得更鲁棒.本文针对二维/三维的三角形/四面体非结构网格提出了数值格式,给出了几个基准测试算例,验证了本文提出的数值方法在采用非结构网格求解不可压粘性流动问题时的精确性和鲁棒性.