欠膨胀超声速射流不稳定性机理的数值研究

应用NND有限差分格式求解轴对称可压缩N-S方程,研究了不同驻室与环境压力比条件下欠膨胀超声速射流近场的失稳特性.计算结果表明欠膨胀超声速射流的失稳机制根据射流激波结构的特征可分为3种失稳模式:具有规则反射激波结构和单一剪切层特征的射流不稳定性;带有马赫反射激波结构和双剪切层特征的射流不稳定性;具有弯曲马赫杆和高度欠膨胀射流的不稳定性.对于欠膨胀超声速射流,沿射流方向重复出现拟周期性的射流激波结构是射流稳定发展的特征,这种射流激波结构的消失是射流开始失稳的标志.

水下超声速气体射流回击现象的实验研究

对水下超声速气体射流的动力学行为进行了实验研究．通过流动可视化揭示了回击现象的演化过程，利用探针排获得了射流近场区的脉动压力分布，实验结果表明：在超声速喷管出口两倍直径处，射流形貌的变化导致气体中出现了大幅值压力脉冲．通过流场可视化与压力测量的同步校验，证实了喷口端面处回击事件与流场气相区中压力脉动之间相关性．

煤油射流在超声速燃烧室中的实验研究

在超声速燃烧室中分别采用气泡雾化煤油与纯煤油射流进行实验,研究不同情况对燃料的雾化和贯穿深度的影响.实验选用纹影法记录实验段图像,拍摄了不同注射压强条件下燃料有无气泡雾化的流场照片,对时间平均流场和瞬态流场分别进行记录.实验结果表明:气泡雾化的确明显地提高了液体燃料的雾化程度,但对贯穿深度没有显著的影响,提高贯穿深度的有效方法是增加射流压强.

超声速反向混合实验及其压力温度测量

对超声速反向射流混合加热方案进行实验验证。实验结果表明：控制向燃烧室注入水雾的流量可以方便地调节燃烧室的温度和压力；用双路氢氧进气系统易于实现稳定的点火和燃烧。用热电偶测量混合前后的流场温度分布的初步结果表明，反向射流混合方案基本可行。

超声速液体射流的气动特性

介绍了有关脉冲超声速水射流以及柴油射流气动特性的研究结果。水射流实验是在一台垂直设置的内径为8mm的火药枪设备上进行的。用出口直径为5mm的喷嘴,产生了速度为600m/s的水射流。用纹影仪观察了射流及激波形状,从而测量了激波与前体驻点之间的离开距离。柴油射流实验是在一台水平设置的高压氦气气枪设备上进行的。

用激波管研究超音速气固两相流

在激波管里进行了可压缩性气固两相流的实验研究。测量了激波通过颗粒群时的压力的衰减过程。用纹影仪拍摄了激波与颗粒群相互干涉的照片。试验了颗粒群的不同构造对压力衰减的影响。指出了激波反射、聚焦等非线性气动因素是可压缩性气固两相流的关键问题。

超音速流动中侧向喷流干扰特性的实验研究

在超音速流动中,进行了侧向喷流干扰特性的实验研究,研究了喷流压力、攻角、迎风侧及背风侧喷流对侧向喷流干扰特性的影响.结果表明,随喷流压力增大,喷流前的高压区向前扩展,喷流的包裹作用加强.有攻角时,背风侧喷流前的高压区更大,喷流包裹作用的影响区域前移,喷流的控制效果更好,这一趋势随攻角的增大更加明显.

甲烷超声速燃烧过程的数值模拟

提出了一种CH_4/O_2在超声速气流中燃烧的6方程化学反应模型，并且用在超声速高温空气中横向喷射的二维流场进行了数值模拟验证。特别模拟了不同来流条件和壁面条件对燃烧效率的影响及CH_4和空气中的氧气混合燃烧的过程。数值方法采用二阶精度的Harten-Yee隐式TVD格式，计算结果表明6方程反应模型能较好地反映CH_4/O_2的燃烧过程。

超音速流动中侧向喷流干扰特性的数值模拟

通过与实验结果的比较验证Fluent软件可以用于超音速流动中侧向喷流干扰特性数值研究．使用Fluent软件对超音速流动中不同喷流压力和攻角下侧向喷流干扰特性进行的数值研究表明，超音速流动中，随喷流压力和负攻角增大，喷流前的高压区明显增大，喷流的控制效果更好．喷流包裹作用的影响范围在90°弹面内．喷流压力增大，喷流包裹作用加强，影响范围增大．

超声速模型燃烧室中气化煤油喷注研究

利用直接照相和纹影显示研究了不同预热温度的煤油喷注到静态大气和马赫数2.5的横向气流时射流结构.煤油加热系统可将0.8kg煤油加热到670K和5.5MPa压力.比较4MPa压力下290K～550K不同温度的煤油射流结构可以发现,550K煤油射流一旦流出立即完全气化,并且保持贯穿深度基本不变.结果表明:喷注汽化燃料有可能改善液体碳氢燃料超声速燃烧室的性能,因为至少省却了雾化和气化过程.

A Multiscale-Domain Decomposition Method for High Reynolds Number Flows

The high Reynolds number flow contains a wide range of length and time scales, and the flow domain can be divided into several sub-domains with different characteristic scales. In some sub-domains, the viscosity dissipation scale can only be considered in a certain direction; in some sub-domains, the viscosity dissipation scales need to be considered in all directions; in some sub-domains, the viscosity dissipation scales are unnecessary to be considered at all. For laminar boundary layer region, the characteristic length scales in the streamwise and normal directions are L and L Re-1/ 2 , respectively. The characteristic length scale and the velocity scale in the outer region of the boundary layer are L and U, respectively. In the neighborhood region of the separated point, the length scale l<supersonic flows over rearward and frontward steps as well as an interaction flow between shock wave and boundary layer were solved numerically. The pressure distributions and local coefficients of skin friction on the wall are given. The numerical results obtained by the multiscale-domain decomposition algorithm are well agreement with those by NS equations. Comparing with the usual method of solving the Navier-Stokes equations in the whole flow, under the same numerical accuracy, the present multiscale domain decomposition method decreases CPU consuming about 20% and reflects the physical mechanism of practical flow more accurately.

Numerical Analyses of Transonic Fluid/Structure interaction in Aircraft Engineering

Through the coupling between aerodynamic and structural governing equations, a fully implicit multiblock aeroelastic solver was developed for transonic fluid/stricture interaction. The Navier-Stokes fluid equations are solved based on LU-SGS (lower-upper symmetric Gauss-Seidel) Time-marching subiteration scheme and HLLEW (Harten-Lax-van Leer-Einfeldt-Wada) spacing discretization scheme and the same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Transfinite interpolation (TFI) is used for the grid deformation of blocks neighboring the flexible surfaces. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between fluid and structure. The developed code was fort validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. In the subsonic and transonic range, the calculated flutter speeds and frequencies agree well with experimental data, however, in the supersonic range, the present calculation overpredicts the experimental flutter points similar to other computations. Then the flutter character of a complete aircraft configuration is analyzed through the calculation of the change of structural stiffness. Finally, the phenomenon of aileron buzz is simulated for the weakened model of a supersonic transport wing/body model at Mach numbers of 0.98 and l.05. The calculated unsteady flow shows, on the upper surface, the shock wave becomes stronger as the aileron deflects downward, and the flow behaves just contrary on the lower surface of the wing. Corresponding to general theoretical analysis, the flow instability referred to as aileron buzz is induced by a stronger shock alternately moving on the upper and lower surfaces of wing. For the rigid structural model, the flow is stable at all calculated Mach numbers as observed in experiment

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郭永怀先生诞辰九十周年纪念文集

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谈镐生文集

本文集收入了著名力学家、应用数学家、中国科学院院士谈镐生先生在流体力学、稀薄气体动力学和应用数学研究领域的论文和研究报告26篇，谈镐生先生倡导和支持力学基础研究的有关文章和论述21篇，谈先生的学术活动和生活图片多幅，以及谈镐生先生生平，最后附有谈先生生平年表。