可压缩流向涡与激波轴对称干扰的数值模拟

用ＮＳ方程数值模拟了可压缩流向涡和激波轴对称相互作用现象。数值模拟包括定常和非定常两种情况,计算结果分别与相应的实验进行了比较,结果表明数值模拟成功地捕捉到了激波和旋涡相互作用过程中发生的激波波面变形,激波振荡,涡核变大以及激波波后出现驻点、回流区等流场特征。提出了判断流向涡与运动激波相互作用中旋涡破碎的准则。     

可压缩流向涡与激波轴对称干扰的数值模拟

用ＮＳ方程数值模拟了可压缩流向涡和激波轴对称相互作用现象．数值模拟包括定常和非定常两种情况,计算结果分别与相应的实验进行了比较．结果表明数值模拟成功地捕捉到了激波和旋涡相互作用过程中发生的激波波面变形,激波振荡,涡核变大以及激波波后出现驻点、回流区等流场特征．提出了判断流向涡与运动激波相互作用中旋涡破碎的准则     

可压缩流向涡与激波轴对称干扰的数值模拟1)

用NS方程数值模拟了可压缩流向涡和激波轴对称相互作用现象.数值模拟包括定常和非定常两种情况,计算结果分别与相应的实验进行了比较.结果表明数值模拟成功地捕捉到了激波和旋涡相互作用过程中发生的激波波面变形,激波振荡,涡核变大以及激波波后出现驻点、回流区等流场特征.提出了判断流向涡与运动激波相互作用中旋涡破碎的准则.     

高压气体冲击流场的数值研究

本文针对高压气体流动产生强冲击波的特点,利用近年来公认较好的高精度、高分辨率总变差不增(TVD)格式对圆柱形高压区气体向大气膨胀过程中产生的冲击流场问题进行了数值模拟。数值试验表明:采用高分辨率的TVD差分格式能够很好地描述高压气体冲击流场的波系结构,且没有出非物理振荡,对激波的分辨率高。     

二维激波与剪切层相互作用的直接数值模拟研究

采用五阶weighed esseritially non-oscillatory (WENO) 格式和三阶total variation diminishing (TVD) Runge-Kutta 格式, 通过求解二维非定常Navier-Stokes 方程, 直接数值模拟了激波与剪切层相互作用, 目的在于揭示激波与剪切层相互作用过程中噪声产生的机理. 研究发现:(1) 当入射激波穿过剪切层时, 剪切层中心位置向下层区域偏移;(2) 入射激波穿过剪切层产生小激波, 在小激波与剪切层接触点处产生声波并向外辐射;(3) 反射激波穿过剪切层后形成了分段弧状激波;(4) 当反射激波穿过剪切层时, 激波在鞍点处泄漏并向外辐射声波, 这是一种激波泄漏机制.     

激波-涡干扰声场的数值研究

采用高精度差分格式求解非定常可压缩Navier-Stokes方程,对激波－单涡／双涡相互干扰产生的声场进行了直接数值。详细研究了波－涡干扰声场结构的早期发展阶段,将激波－单涡的计算结果和相应实验进行 对比,并给出近场声压的衰减规律。在此基础上模拟较为复杂的激波－双涡干扰,给出不同旋涡旋转方向下的声场结构。     

TVD自相容流体力学拉氏格式研究

流体力学数值模拟格式总体上可分为Eulerian(欧氏)、Lagrangian(拉氏)和ALE(Arbitrary LagrangianEulerian),TVD广泛应用于Eulerian格式。本文利用具有TVD保持性质的Runge-Kutta型时间离散方法,构造了流体力学Lagrangian(拉氏)自相容格式,应用von Neumann小扰动技术分析了该格式的稳定性,并进行了相应的数值模拟,较好地抑制了激波波后非物理振荡。     

翼型、机翼非定常运动模式下动态数值模拟

基于RANS方程,通过刚性动网格技术实现对翼型和机翼典型运动模式的描述,采用双时间推进方法和Roe空间离散格式对流场求解,构建了一个非定常气动计算平台;以NACA0012翼型为算倒进行了动态数值模拟可信度验证。数值模拟结果与试验数据吻合较好,升力和俯仰力矩的最大计算误差分别为3％和10％,表明了该平台的可靠性。另外,还数值模拟了M6机翼的动态非定常流场,并分析了两种湍流模型对非定常流场激波的捕捉能力。结果表明非定常流动中S-A湍流模型对激波的捕捉较B-L模型更敏感。文中开发的非定常计算平台对进一步解决三维复杂流场的流动问题有很高的工程应用价值。     

高温激波管化学非平衡流动数值模拟研究

为了预测氢氧定容燃烧驱动的高温激波管性能,需要准确分析激波管非定常化学非平衡流动过程.本文在破膜前的驱动段定容燃烧以及破膜后的化学非平衡流动数值模拟中,引入双时间步长方法,发展高温激波管化学非平衡流动数值模拟方法,该方法在时间上具有二阶精度.计算结果与目前存在的激波管流动解析解以及零维化学反应系统的数值解进行了比较,吻合较好.对于典型高温激波管状态,采用有限体积方法离散准一维流动Euler控制方程,并通过将流动过程和化学反应动力学过程耦合求解,获得了激波管内部的化学非平衡流动特征.     

非定常流动的快速拉格朗日涡方法数值模拟

采用快速拉格朗日涡方法数值模拟有复杂旋涡运动的非定常流动. 利用离散涡元模拟旋涡的产生、聚集和输送过程. 拉格朗日描述法用来计算离散涡元的移动,而移动速度则利用广义毕奥-萨伐尔公式结合快速多极子展开法计算,修正的涡半径扩散模型用来模拟离散涡元的黏性扩散. 突然起动圆柱和大攻角下突然起动翼型的非定常有涡流动的数值模拟,及其与试验结果的对比验证了方法的有效性. 另外,大攻角下突然起动翼型的计算结果给出了翼型起动后吸力面旋涡的产生、发展,周期性非定常流动的形成,以及尾流旋涡结构等一些重要的流动特征.[关键词] 非定常流有涡流动快速涡方法      

可压缩流向涡与反向运动激波相互作用的实验

对可压缩流向涡与反向运动激波相互作用的现象进行了实验研究．实验在９４ｍｍ×９４ｍｍ的方截面激波管中进行．在实验段上游安装了一个有限翼展平直机翼．当入射激波通过机翼后，波后２区气流在模型翼尖诱导出一条流向涡．入射激波在激波管端壁反射后，形成的反射激波在观察窗处和流向涡发生作用．实验中拍摄了激波与流向涡作用全过程的纹影照片，观察到了一些和定常激波与旋涡相互作用不同的现象，并与数值计算结果进行了初步比较     

激波与涡对相互作用的实验研究

在方截面激波管中进行了平面运动激波和涡对的二维相互作用实验，研究了激波与同向涡对、激波与反向涡对相互作用的非定常过程．根据实验照片，分析讨论了作用过程中激波的变形，二次激波和三波点的形成、演变，激波与激波的相互作用，以及旋涡结构的变化等．实验表明，激波通过涡核时，激波发生剧烈变形，旋涡强度增大，涡核形状改变．     

Interaction of a Streamwise Vortex with an Oblique Shock Wave

Interaction of a supersonic streamwise vortex with an oblique shock wave is considered. A mathematical model of the streamwise vortex is constructed. Three interaction regimes (weak, moderate, and strong) are found. It is shown numerically that vortex breakdown is possible in the case of strong interaction. The influence of the governing parameters on the interaction type is studied. It is shown that the main effect on the interaction type is exerted by the streamwise velocity and angle of the wedge forming the shock wave. The effect of splitting of the primary vortex on the shock wave in the case of moderate and strong interaction regimes is found.     

STUDY ON THE FUEL AIR MIXING INDUCED BY A SHOCK WAVE PROPAGATING INTO A H_2-AIR INTERFACE

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激波在平板上诱导的旋涡强度的测量

运动激波通过两个等攻角平板后诱导出两个同向旋转的旋涡，这两个旋涡在随当地气流向下游运动的同时，绕涡核连线中心旋转。本文通过测量涡对的转动角度速度，获得了每个旋涡的强度。实验结果表明，由此测得的旋涡强度不同用于小攻角平板起动涡公式计算了起动涡强度。     

The shock–vortex interaction patterns affected by vortex flow regime and vortex models

We have used a third-order essentially non-oscillatory method to obtain numerical shadowgraphs for investigation of shock–vortex interaction patterns. To search different interaction patterns, we have tested two vortex models (the composite vortex model and the Taylor vortex model) and as many as 47 parametric data sets. By shock–vortex interaction, the impinging shock is deformed to a S-shape with leading and lagging parts of the shock. The vortex flow is locally accelerated by the leading shock and locally decelerated by the lagging shock, having a severely elongated vortex core with two vertices. When the leading shock escapes the vortex, implosion effect creates a high pressure in the vertex area where the flow had been most expanded. This compressed region spreads in time with two frontal waves, an induced expansion wave and an induced compression wave. They are subsonic waves when the shock–vortex interaction is weak but become supersonic waves for strong interactions. Under a intermediate interaction, however, an induced shock wave is first developed where flow speed is supersonic but is dissipated where the incoming flow is subsonic. We have identified three different interaction patterns that depend on the vortex flow regime characterized by the shock–vortex interaction.      

数值研究平板方舵激波-湍流边界层干扰

数值研究了平板方舵激波-湍流边界层干扰流场。模拟出了分离激波与弓型激波砬撞后形成的“λ”激波结构;消晰地显示了分离区中的旋涡结构,发现流场中会出现二次分离涡,并从理论上分析了流场对称面涡心形态与非定常的关系,得到了涡心为不稳定螺旋点或出现极限环是非定常流动特征的新结论。     

Computational study of curved shock–vortex interaction

The interaction between a curved shock wave and a compressible vortex is numerically investigated. The investigation concentrates on the local deformation of the shock structure due to the shock–vortex interaction. The essentially non‐oscillatory (ENO) scheme is used to solve the unsteady two‐dimensional Euler equations. A curved shock wave is obtained by the diffraction of an initially planar shock wave around a right‐angled corner and then allowed to interact with a strong compressible vortex superimposed on the flow. The same vortex affects the shock wave differently depending on the placement of the vortex because of the varying strength of the shock wave. This effect could range from a non‐symmetric deformation of the shock wave to a local disruption in the shock structure depending on the strength of the shock wave in the interaction region. This process leading to a local disruption in the shock structure is analyzed in detail. It is shown that such a disruption in the shock structure can be predicted by simple one‐dimensional considerations. Copyright © 1999 John Wiley & Sons, Ltd.     

A comparison of four recent numerical schemes giving high resolution of shock wave and concentrated vortex

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Existence criteria for reflection configurations in shock–vortex interactions

The length scale criteria is widely accepted as an explanation for transition and hence existence of different shock wave reflection configurations in pseudo-steady flows. However, there has not been any attempt to validate this criteria using information obtained from a time-dependent numerical simulation. A high resolution time-dependent numerical simulation in pseudo-steady flow is carried out in the present work. Time-dependent numerical data is used to calculate flow features in a laboratory frame of reference to verify validity of the length scale criteria for existence of different shock wave reflection configurations in pseudo-steady flow. This analysis is then extended to the study of unsteady shock wave reflection configurations in shock–vortex interactions. It is shown that the existence of regular reflection (RR) and Mach reflection (MR) configurations in an unsteady flowfield resulting from shock–vortex interactions can also be explained locally based on limiting conditions similar to that prescribed by the length scale criteria for pseudo-steady flow.

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