基于CFD/CSD技术的压气机叶片流固耦合及颤振分析

针对叶片故障的原因颤振问题,基于计算流体动力学/计算结构力学(CFD/CSD)耦合算法,研究了压气机典型叶片的流固耦合(FSI)问题及颤振特性.使用有限体积法求解非定常三维Navier-Stokes方程和有限元法求解三维结构体模型,在两个求解器间由载荷转换、网格变形传递和同步化方法完成数据交换及求解.以高性能风扇NAS...     

RPC-IES: The Ion and Electron Sensor of the Rosetta Plasma Consortium

The ion and electron sensor (IES) is part of the Rosetta Plasma Consortium (RPC). The IES consists of two electrostatic plasma analyzers, one each for ions and electrons, which share a common entrance aperture. Each analyzer covers an energy/charge range from 1 eV/e to 22 keV/e with a resolution of 4%. Electrostatic deflection is used at the entrance aperture to achieve a field of view of 90°× 360° (2.8π sr). Angular resolution is 5°× 22.5° for electrons and 5°× 45° for ions with the sector containing the solar wind being further segmented to 5°× 5°. The three-dimensional plasma distributions obtained by IES will be used to investigate the interaction of the solar wind with asteroids Steins and Lutetia and the coma and nucleus of comet 67P/Churyumov–Gerasimenko (CG). In addition, photoelectron spectra obtained at these bodies will help determine their composition.     

超音速射流与弹体绕流干扰流场数值分析

绕弹体的超音速气流与火箭发动机燃气喷流相互作用，在弹体底部形成了复杂的干扰流场。本文应用了四阶的ＭＵＳＣＬ ＴＶＤ格式，求解雷诺平均的Ｎ－Ｓ方程，对这一复杂流动进行了数值模拟，得到了流场结构随不同喷口压力的变化规律。     

DLC 和CrN 薄膜在油润滑下的摩擦性能

采用闭合场非平衡直流磁控溅射技术和阴极电弧离子镀技术在轴承钢表面分别制备了DLC 和

CrN 薄膜,在全配方发动机油(CF-4,15W/40)润滑条件下,选择DLC/ 钢、CrN/ 钢摩擦配副,用SRV-IV 摩擦实

验机考察了25℃和100℃时DLC 与CrN 薄膜在不同载荷下的摩擦因数和磨损率,并对摩擦界面进行分析。结

果表明:DLC 和CrN 薄膜在油润滑条件下的摩擦因数都随着载荷的增加而降低;DLC 和CF-4 构成的固液复合

润滑体系具有更加优异的摩擦学性能;活性较高的CrN 薄膜与发动机油中的添加剂相互作用,在摩擦界面上

发生摩擦化学反应形成摩擦化学反应膜,并且薄膜表面形成的氧化层有利于提高薄膜在高温时的耐磨性。

     

进气道中激波-边界层干扰特性研究

针对高超进气道中激波/边界层干扰等现象,选取了24°压缩拐角及二维高超进气道DLR-GK01等算例,比较研究了混合网格并行数值模拟软件中SA、SST、TNT三种湍流模型对激波/边界层干扰等现象的模拟能力,主要考察了不同湍流模型对流场结构、壁面压强以及壁面摩阻的影响。结果表明:三种湍流模型在模拟大分离流场时存在不同的流动分离特性,TNT湍流模型较SST和SA湍流模型模拟的分离起始位置、分离区大小及边界层厚度与实验吻合度最好。     

不同几何调节位置上的单边膨胀喷管流固耦合计算

为了获得高超声速飞行器非设计点上较好的性能,包括单边膨胀喷管(SERN)在内的几何可调方案成为了目前研究的热点,针对单边膨胀喷管开展了流固耦合的研究,重点分析流固耦合中的动态载荷问题,不考虑结构传热及重力的影响,对不同几何调节位置上的SERN开展了计算分析.结果表明在不同位置上,SERN唇口板均出现了超声速颤振.通过进一步分析,获得结论如下:(1)唇口板振动特点主要由材料属性和结构决定;(2)唇口板在不同调节位置上,振动频率大致均为结构的一阶振动频率,喷管升力的振荡范围较喷管推力的振荡范围大;(3)随着唇口板角度的增加,唇口板振幅增大.     

跨声速风扇叶片反扭影响因素研究

基于结构几何非线性大变形的静态分析和流场分析,使用叶片反扭设计的流固双向耦合的数值模拟方法,得到NASA Rotor67跨声速风扇叶片的冷态加工叶型。研究了材料、气动工况、转速对叶片静态变形和反扭设计参数的影响。结果表明:转速对叶片反扭的影响最显著,气动工况次之,材料的影响最弱;另外,这三种因素和叶片反扭的关系,与其和叶片静变形量的关系有较大相关性。     

Interaction of magnetoacoustic solitons in electron-positron plasmas

The interaction between two, four and six magnetoacoustic solitons in electron-positron plasmas are investigated. The extended Poincaré–Lighthill–Kuo (PLK) perturbation method is employed to derived two KdV equations for magnetoacoustic solitons moving towards each other and studied the head-on collision between them and their phase shifts. The Hirota bilinear method is used to have multi-soliton solutions of already derived two KdV equations for right and left moving solitons. The four and six magnetoacoustic solitons solutions of the two KdV equations are obtained to discuss their interaction and phase shifts. It is found that only compressive magnetoacoustic solitons structures are formed in electron-positron plasma. The present study may be useful to understand the collective phenomena related to head-on and overtaking magnetoacoustic solitons interaction in electron-positron plasmas that may occur in a pulsar magnetosphere.     

Review of theoretical achievements for starting flow problem for all Mach numbers

The typical behavior of unsteady flow and force evolution in a number of applications, such as aero-elastics, gust-wing interaction, flapping flight and flight maneuvering, can be understood using the starting flow model. Starting flow model is obtained either by setting rapidly an angle of attack for a wing moving at constant speed, or by accelerating a wing to a constant speed while gaining an angle of attack. In the limiting case of impulsively starting flow, the wing is assumed to gain suddenly an angle of attack in an initially uniform flow. Theories have been developed for impulsively starting flow at small angle of attack long before and at large angle of attack only recently, especially for incompressible and supersonic flow. This paper intends to provide a state-of-art overview of the typical flow phenomena, force evolution characteristics and developed theories for impulsively starting flow at any angle of attack and for both lower speed flow (vortex dominated) and high speed flow (compressible wave dominated). This review also provides some new topics that deserve further studies.     

Shock/shock interactions between bodies and wings

This paper examines the Shock/Shock Interactions (SSI) between the body and wing of aircraft in supersonic flows. The body is simplified to a flat wedge and the wing is assumed to be a sharp wing. The theoretical spatial dimension reduction method, which transforms the 3D problem into a 2D one, is used to analyze the SSI between the body and wing. The temperature and pressure behind the Mach stem induced by the wing and body are obtained, and the wave configurations in the corner are determined. Numerical validations are conducted by solving the inviscid Euler equations in 3D with a Non-oscillatory and Non-free-parameters Dissipative (NND) finite difference scheme. Good agreements between the theoretical and numerical results are obtained. Additionally, the effects of the wedge angle and sweep angle on wave configurations and flow field are considered numerically and theoretically. The influences of wedge angle are significant, whereas the effects of sweep angle on wave configurations are negligible. This paper provides useful information for the design and thermal protection of aircraft in supersonic and hypersonic flows.