攻角拉起时前体非对称涡诱导机翼摇滚运动

针对目前前体非对称涡诱导机翼摇滚研究时攻角往往处于静态而没有考虑攻角动态拉起的问题,在北航D4风洞中采用细长旋成体与30°后掠翼的组合体模型,通过不同拉起速度下的机翼摇滚运动实验,分析了攻角拉起速度对前体非对称涡诱导机翼摇滚运动的影响及影响产生的原因;随后通过在快速拉起摇滚运动过程中进行模型表面压力测量,研究了快速拉起机翼摇滚的流动机理.实验结果表明,由于机翼摇滚运动的时间随攻角拉起速度增加而减少,使得在3个不同的拉起速度分区内,摇滚运动呈现为不同的运动形态,其中第3个快速拉起分区内的摇滚运动为与攻角静态时完全不同的类正弦摇滚运动形态.与攻角静态时机翼摇滚的流动机理不同,快速拉起时这种类正弦摇滚运动主要源于前体非对称涡随攻角的演化,前体非对称涡随滚转角的涡型切换不再重要.      

Film cooling performance and flow structure of single-hole and double-holes with swirling jet

This paper presents the results of a numerical study of the effects of swirling flow in coolant jets on film cooling performance. Some combined-hole designs with swirling coolant flow entering the delivery hole are proposed and analyzed. Adiabatic film cooling effectiveness values for cases with various blowing ratios are compared. Detailed flow structures and underlying mechanisms are discussed. The results show that film cooling effectiveness is improved with jet swirl at high blowing ratios, ...     

横向荷载作用下RC多T梁上部结构的受力性能

基于实体退化壳单元理论,采用分层单元模拟了混凝土和构造钢筋,采用组合单元模拟了受力纵筋;并利用弥散裂缝模型、关联流动法则和Madrid强化准则等来描述了混凝土的材料非线性,推导了非线性薄壁壳单元的统一单元模式,研究了横向荷载作用下RC多T粱上部结构的裂缝发展和钢筋屈服等性能.结果表明,RC多T梁的主梁先于横隔板开裂,与偏载加载或中载加载的加载方式无关;横隔板开裂削弱整体横向联系,使主梁协同受力性能减弱,受载较大的主粱荷载横向分布系数略趋于不利变化;偏载加载至结构破坏时,部分主粱的纵向受力钢筋已进入塑性阶段,而中载加载至结构破坏时,所有主粱的纵向受力钢筋均进入塑性阶段.所得结论为多T梁设计提供参考.     

马赫数2.5超/亚声流流向涡掺混超燃室冷态实验

结合对应的数值计算,对一种带亚声速预燃室和流向涡掺混器的超声速燃烧模型燃烧室实验台,在其进口马赫数为2.5的来流条件下,进行了冷态流场的实验研究.实验测得其壁面静压分布和激波系结构与流场的CFD计算结果基本一致.实验结果表明,模型燃烧室全流场超声速,达到设计状态.马赫数2.5下的冷态实验数据和CFD计算数据为进行点火实验提供了依据.      

复合材料层板在弹性支持下的非线性稳定性

利用能量变分原理和非线性几何方程，建立具有弹性约束的复合材料层板，在面内载荷作用下的非线性稳定性控制方程组，通过运用广义傅里叶级数法对控制方程组进行求解，得到相应的截荷－中心挠度曲线。计算结果表明：非对称层合板在面内载荷作用下，一般产生的是向变形，但在一定的铺层顺序，边界条件、受载方式等情况下，也可能发生分叉型屈曲。     

TYPES OF FLOW OVER LEESIDE OF A SLENDER TAPERED WING AT SUPERSONIC SPEED

ＴＹＰＥＳＯＦＦＬＯＷＯＶＥＲＬＥＥＳＩＤＥＯＦＡＳＬＥＮＤＥＲＴＡＰＥＲＥＤＷＩＮＧＡＴＳＵＰＥＲＳＯＮＩＣＳＰＥＥＤＨｏｎｇＪｉｎｓｅｎ（ＢｅｉｊｉｎｇＩｎｓｔｉｔｕｌｅｏｆＡｅｒｏｎａｕｌｉｃｓ，Ｂｅｉｊｉｎｇ，Ｃｈｉｎａ，１０００７４）Ａｂｓ...     

叶轮机转子内流动的三维跨声速Navier-Stokes方程组数值计算及试验验证

应用有限体积法及Baldwin-Lomax代数湍流模型求解叶轮机转子内流动的三维可压缩非定常薄层Navier-Stokes方程组,计算一个绕X轴等转速旋转的转子内流场问题,用当地时间步长方法来加速收敛.采用隐式算法对对流通量进行求解,而耗散通量采用显式算法.采用高阶TVD下的Roe格式计算对流通量,采用中心差分格式计算耗散通量.关于守恒变量Q的非线性方程组,采用牛顿迭代方法求解,线化后的方程用对称的Gauss-Seidle方法求其渐近解.应用该算法模拟了转子Rotor67流场,与试验做了大量的对比研究,包括性能、等马赫线以及总压和总温等.在最高效率点附近计算与试验比较接近,但在靠近失速点时计算与试验有较大的差别.     

细长体大迎角绕流的滚转角特性

尖拱和钝拱细长体的截面侧向力分布呈现明显的滚转角效应。不同滚转角下尖拱侧向力沿轴向分布曲线(CC～x/D)的相位和半周期各不相同,截面侧向力随滚转角变化(CC～)呈现一定的无规律性;而钝拱CC～x/D曲线的相位和半周期基本相同,但振幅值大小依赖于滚转角,CC～分布呈完全的无规律性。尖拱模型头部的加工精度导致的微扰动使得尖拱CC～x/D分布变成型式基本一致的两簇曲线,其特征点和半周期分别对应相同,CC～分布呈现典型的双周期方波。     

迎角变化对细长旋成体绕流非定常压力脉动特征的影响

在亚临界流动范围内,通过对尖拱细长旋成体在无侧滑状态下的烟线显示和脉动压力测量试验,揭示了迎角α从0°向90°变化过程中细长体绕流依次经历了四种背涡流动结构:附着流动、对称二涡结构、非对称多涡结构和混合背涡结构.压力的脉动幅度在附着流动和对称二涡结构中沿轴向基本保持不变,在非对称多涡结构中是沿轴向增长的,而在混合背涡结构中却变为沿轴向减少.压力脉动频率值在非对称多涡结构中是沿轴向减少的,而在混合背涡结构中却是沿轴向增长的.     

Non-Linear Growth of Trapped Particle Modes in Linearly Stable, Current-Carrying Plasmas – A Fundamental Process in Plasma Turbulence and Anomalous Transport

The two-stream instability as a fundamental process in a current-carrying plasma is reconsidered. Its well-established linear version, based on kinetic Landau theory, predicts a threshold for the drift velocity between both species below which the plasma should be stable. We report on simulations which, however, show that a plasma as a non-linearly responding medium can be destabilized well below this threshold. Responsible for this unexpected behaviour are coherent, electrostatic, trapped particle structures such as phase space vortices or holes which can grow non-linearly out of thermal noise receiving their energy from the net imbalance of loss of electron kinetic energy and gain of ion kinetic energy. The birth of predominantly zero-energy holes is shown numerically being associated with initial, non-topological fluctuations. The latter are not subject to Landau damping, as they lie outside the realm of linear wave theory. For a pair plasma a typical scenario is presented, which encompasses several regimes such as non-linear growth of multiple holes, saturation and fully developed structural turbulence as well as an asymptotic approach to a new collisionless equilibrium. During the transient, structural state the plasma transport appears to be highly anomalous.