A swept fin-induced flow field with different height mounting gaps

In order to apply the air fin successfully and ensure the maneuverability of hypersonic vehicle, a key problem to be studied urgently is the heat flux brought by the fin mounting gap. The appearance of mounting gap and fin shaft can induce many complex flow structures which need more attentions to be investigated. Under Ma 6, Nano-tracer-based Planar Laser Scattering (NPLS) and Temperature Sensitive Paints (TSP) were applied to visualize and measure transient flow structures and heat flux distribution of a swept fin-induced flow field with different height mounting gaps. Complementarily, Reynolds-averaged N-S equations were solved with k-ω SST turbulent model. The heat flux distribution results of numerical simulation and TSP observed the change of high heat flux region with different mounting gap, both in position and magnitude. The streamlines based on Computational Fluid Dynamics (CFD) and flow visualization results obtained by NPLS revealed the cause of high heat flux region. The high heat flux region in this flow field is mainly related to the reattachment of vortex and flow stagnation. The increase of gap height can lead to stronger gap overflow and shaft-induced horseshoe vortex, which are source of the high heat flux around the fin. The case with the highest mounting gap (4 mm) en-counters the most severe aerodynamic heating, both on the surface of fin and plate. Thus, under the premise of ensuring the flexibility of the fin, the gap should be set as small as possible.     

悬停状态倾转旋翼/机翼干扰流场及气动力的CFD计算

基于一套高效通用的多层运动嵌套网格技术,建立了适合悬停状态倾转旋翼机旋翼/机翼气动干扰特性分析的高效混合计算流体力学（CFD）方法。在倾转旋翼/机翼贴体网格区采用可压雷诺平均Navier-Stokes（RANS）方程作为主控方程,过渡/背景网格区选用Euler方程,湍流模型选用Spalart-Allmaras模型。时间推进上采用双时间推进格式进行非定常求解,并在方法中运用了SPMD（Single Program Multiple Data）模式的并行加速技术。在此基础上,首先分别采用UH-60A直升机旋翼及XV-15倾转旋翼机旋翼作为数值算例,验证了CFD方法的有效性。然后着重对倾转旋翼/机翼的非定常干扰流场及气动力分布特征进行了数值研究,模拟得到与实际情况相符的“喷泉效应”干扰现象。计算结果表明,干扰作用使得倾转旋翼相对于孤立旋翼拉力数值减小了3%,但总的拉力系数损失达到了17%,证明悬停状态下气动干扰对飞行器气动性能有重要影响。     

基于CFD/CSD方法的蜻蜓柔性翼气动特性分析

给出了一种基于计算流体力学/计算结构力学（CFD/CSD）的双向流固耦合方法.通过交替数字二叉树（ADT）搜索技术识别流固网格之间的宿主-受体关系.采用局部插值算法完成两套网格系统之间的数据交换,并使用Delaunay图映射方法来完成气动网格的移动.将自编的非线性结构有限元程序、接口程序与南京航空航天大学（NUAA）微型飞行器中心的流体计算程序3D2MUFS相连接,应用于蜻蜓柔性翼拍动飞行的气动计算中.计算结果表明:柔性变形使得蜻蜓翼的时均举力系数从0.31提高到0.53,时均推力系数从0.07提高到0.13,证实了柔性变形能改善扑翼的气动性能.      

"伙伴交际法"在高职英语教学中的应用

口头表达能力作为语言综合能力的重要体现之一,在教学中应受到高度重视。然而在我国传统的公共英语教学中,“轻听说、重读写”的倾向造成了不少学生渎写尚可,但张口即结舌的状况。笔者将“伙伴交际法”应用到教学实践中,有效地提高口语教学质量,值得推而广之。     

A Revisit of the Phobos Events

The magnetic field disturbances detected by the Phobos-2 spacecraft in 1989 have been suggested to be caused by a ring of dust and/or gas emitted from the Martian moon, Phobos. The physical nature of these ``Phobos events' is examined using results from related investigations over the last twenty years. It is concluded that there is no clear evidence at present to support the association of magnetic field disturbances in the solar wind with Phobos. The situation will be further clarified taking advantage of the multi-spacecraft observations of the Yinghuo-1(YH-1), Mars Express and MAVEN missions beginning in 2012. It is expected that many novel features of solar wind interaction with Phobos (and possibly also Deimos) itself will also be revealed.      

WAKE GEOMETRY CALCULATIONS FOR TILT-ROTOR USING VISCOUS VORTEX METHOD

A tilt-rotor unsteady flow analytical method has been developed based upon viscous vortex-particle meth- od. In this method, the vorticity field is divided into small assembled vortex particles. Vortex motion and diffusion are obtained by solving the velocity-vorticity-formed incompressible Navier-Stokes equations using a grid-free La- grangian simulation method. Generation of the newly vortex particles is calculated by using the Weissinger-L lifting surface model. Furthermore, in order to significantly improve computational efficiency, a fast multiple method （FMM） is introduced into the calculation of induced velocity and its gradient. Finally, the joint vertical experimen- tal （JVX） tilt-rotor is taken as numerical examples to analyze. The wake geometry and downwash are investigated for both hover and airplane modes. The proposed method for tilt-rotor flow analysis is verified by comparing its re- sults with those available measured data. Comparison indicates that the current method can accurately capture the complicated tilt-rotor wake variation and be suitable for aerodynamic interaction simulation in complex environ- ments. Additionally, the aerodynamic interactional characteristics of dual-rotor wake are discussed in different ro- tor distance. Results show that there are significant differences on interactional characteristics between hover mode and airplane mode.     

航空发动机压气机声共振现象初探

航空发动机压气机声共振机理十分复杂,涉及到“气动-结构-声学”的多物理场耦合问题,能导致压气机叶片疲劳破坏,危害巨大,近年来已经成为国外压气机气动、振动、声学领域的研究热点。综述了国外流体诱发腔体发声机理的研究进展,分析了国外航空发动机压气机声共振的研究现状,总结了单级、多级压气机声共振现象的主要特征,并结合中国某型压气机的试验结果,进行了气动、振动、噪声等物理参数的特征分析,认为某型压气机虽然存在着某些独特的问题需要深入研究,但其故障特点与近年来国外开展的声共振现象具有很强的相似性,即认为该型压气机工作中可能存在声共振现象。     

多喷流干扰级间热环境风洞试验研究

运载火箭级间热分离过程中,级间段受高温高压喷流的影响,所处环境恶劣,研究级间热环境中压力、温度和热流分布规律对级间段结构的优化具有重要意义。在Ф1m高超声速风洞中,采用以微型固体火箭燃气为喷流介质的热喷流模拟技术,模拟了运载火箭二级主发动机和四个游动发动机同时工作多喷流干扰条件下的级间热环境,并对级间压力、温度和热流测量试验技术进行了研究,获得了不同级间距、不同排燃窗开口数量情况下的二级底封头和一级前封头表面的热流、温度及压力分布特性。试验结果表明,级间距越小,分离环境越恶劣,压力、温度、热流分布越不均匀;总排燃面积保持不变,排燃窗开口数量变化,对一级前封头上的压力、温度、热流影响不大,但对二级底封头影响较为明显,随着开口数量的减少,二级底封头上压力、温度、热流值均有所增大。本项试验采用同轴热电偶测量了级问区域的热流,热流结果精准度的提高以及热流模拟准则还需进一步探索和研究。     

Numerical study of compression corner flowfield using Gao-Yong turbulence model

A numerical simulation of shock wave turbulent boundary layer interaction induced by a 24° compression corner based on Gao-Yong compressible turbulence model was presented.The convection terms and the diffusion terms were calculated using the second-order AUSM (advection upstream splitting method) scheme and the second-order central difference scheme,respectively.The Runge-Kutta time marching method was employed to solve the governing equations for steady state solutions.Significant flow separation-region which indicates highly non-isotropic turbulence structure has been found in the present work due to intensity interaction under the 24° compression corner.Comparisons between the calculated results and experimental data have been carried out,including surface pressure distribution,boundary-layer static pressure profiles and mean velocity profiles.The numerical results agree well with the experimental values,which indicate Gao-Yong compressible turbulence model is suitable for the prediction of shock wave turbulent boundary layer interaction in two-dimensional compression corner flows.      

立楔诱导高超声速分离流动的被动控制研究

双模态超燃冲压发动机由于压力扰动可能发生不起动现象,造成推力严重下降,对飞行稳定性与飞行安全具有很强的破坏性.不起动初始阶段主要受到激波与边界层相互作用引起的流动分离影响,希望通过控制分离达到改善流动的目的.采用5阶特征型WENO(weighted essentially non-oscillator)格式与3阶TVD(total variation diminishing)型Runge-Kutta(R-K)格式的高精度数值方法,求解三维Navier-Stokes(N-S)方程,研究与分析了凸起物和被动吹吸两种被动控制方法对激波与边界层相互作用导致的高超声速流动分离现象的控制效果.结果表明:凸起物通过诱导流向涡形成,改变空间压力分布,减弱二次分离,影响分离结构;吹吸方式的被动控制技术通过平衡分离区与再附区之间的高低压差,降低逆压梯度,使压力分布与分离区域发生改变.