基于变分模态分解的壁湍流拟序结构形态研究

应用多分量准二维变分模态分解技术,对直接数值模拟的湍流边界层的流向-法向平面进行了分解。通过对从低雷诺数到中等雷诺数(Reτ=400~1750)各个工况的瞬时流场的观察,定性地得到了不同模态所对应的物理结构特征。通过两点相关云图形态和倾斜角度的比较,定量地对比了不同模态对应的拟序结构倾角随法向高度的变化。一阶模态主要对应大尺度扫掠/喷射事件,第二阶模态则对应近壁流向涡结构。两阶模态的拟序结构倾角随法向高度的变化趋势与雷诺数呈弱相关,表明大小尺度模态的几何特征在所研究的雷诺数范围内存在自相似性。     

Direct numerical simulation of impinging shock wave and turbulent boundary layer interaction over a wavy-wall

The interaction of an impinging oblique shock wave with an angle of 30° and a supersonic turbulent boundary layer at Ma_∞=2.9 and Re_θ = 2400 over a wavy-wall is investigated through direct numerical simulation and compared with the interaction on a flat-plate under the same flow conditions. A sinusoidal wave with amplitude to wavelength ratio of 0.26 moves in the streamwise direction and is uniformly distributed across the spanwise direction. The influences of the wavy-wall on the interaction, including the characterization of the flow field, the skin-friction, pressure and the budget of turbulence kinetic energy, are systematically studied. The region of separation grows slightly and decomposes into four bubbles. Local peaks of skin-friction are observed at the rear part of the interaction region. The low-frequency shock motion can be seen in the wall pressure spectra. Analyses of the turbulence kinetic energy budget indicate that both diffusion and transport significantly increase near the crests, balanced by an amplified dissipation in the near-wall region. Proper orthogonal decomposition analyses show that the most energetic structures are associated with the separated shock and the shear layer over the bubbles. Only the bubbles in the first two troughs are dominated by a low-frequency enlargement or shrinkage.     

Layer-oriented Element Integration Algorithm of Conformal Perfectly Matched Layer

As an efficient artificial truncating boundary condition, conformal perfectly matched layer (CPML) is a kind of multilayer anisotropic absorbing media. To reduce computing effort of CPML, this article proposes a layer-oriented element integration algorithm. In this algorithm, the relative dielectric constant and permeability are considered as constants for each the very thin monolayer of CPML, and the element integration of multilayer along the normal direction is substituted by the element integration of monolayer. The CPML is divided into multilayer elements, whose element matrixes are evaluated by monolayer integration. Numerical examples show that the layer-oriented element integration algorithm is reliable and the CPML formed with this algorithm possesses high-efficient absorbing performance.     

微型涡流发生器控制超临界翼型边界层分离实验研究

在低速风洞中研究了微型涡流发生器对超临界翼型边界层分离的控制。根据超临界翼型边界层分离特性，提出了涡流发生器的流动机理。研究了梯形涡流发生器不同高度和弦向位置对边界层分离控制效果的影响。研究表明，微型涡流发生器对超临界翼型边界层分离的控制主要起减阻作用；适宜采用微型涡流发生器对超临界翼型边界层分离进行控制，其最佳位置应在分离线前2～5日涡流发生器高度之间。     

卫星光学遥感系统优化设计与像质评价探讨

介绍了卫星光学遥图像获取与图像处理一体化优化设计的思路；运用通用像质方程（GIQE）对于利用小相对孔径光学系统和调制传递函数补偿（MTFC）方法得到的图像的品质与利用相对较大相对孔径光学系统得到的图像的品质进行了对比分析。     

沟槽面湍流边界层湍流度分布

应用激光测速(LDV)技术对沟槽面湍流边界层湍流度分布进行了精细的测量,实验结果表明,在湍流边界层区域沟槽面湍流度最大值比光滑面要小,但出现的位置比光滑面要远.此外,紧靠沟槽面,即y++<4内,沟槽面有较大的湍流度,说明沟槽面有使近壁区流动紊动增加的趋势.对于y/δ≥0.06的区域,湍流度可用u′\u=2.3 exp (-0.9y/δ)描述,而在y/δ<0.06内,则有u′/u =36.4y/δ.     

Microphysics: Equation of State

The equation of state is one of the three fundamental ingredients used to construct stellar models. The plasma of the interiors of stars such as the Sun is only slightly non-ideal. However, the extraordinary accuracy of the helioseismological data requires refined equations of state. It turned out to be necessary to include a Coulomb correction, commonly evaluated in the Debye-Hückel approximation. Higher-order non-ideal effects have implications as well, both for plasma physics and for solar physics. As a typical example, the recently studied thermodynamic consequence of excited states in compound particles is discussed. This effect is of considerable relevance in the helioseismic determination of the helium abundance in the solar convection zone. This revised version was published online in June 2006 with corrections to the Cover Date.     

On the Composition of the Solar Interior Rapporteur Paper I

Standard solar models, although they are free from the influence of much of the fluid motion that is bound to be present in the Sun, have been shown by helioseismology to represent the spherically averaged structure of the Sun amazingly well. This state of affairs has come about after painstaking refinements by a great many people of the pertinent microphysics, including that which controls the equation of state, the opacity, the nuclear reaction rates and the diffusion that inhibits gravitational segregation of chemical elements. It has instilled confidence in the modellers in being able to predict the composition of the solar interior. But there are consequences of the flow, related particularly to redistribution of chemical species, that can be difficult to identify observationally, yet which may degrade any inferences we might make. Their potential presence must at least be acknowledged by anyone who tries to asses the reliability of the models. This report summarizes the discussions in the preceding pages of this volume of the current theoretical and observational status of the subject, pointing to many of the caveats that have been raised, and attempting at the same time to put them into a seemingly coherent discourse in the context of our present understanding of the workings of the solar interior. This revised version was published online in June 2006 with corrections to the Cover Date.     

二维欧拉方程高分辨正性保持差分格式

针对二维欧拉方程研究了一类高分辨正性保持波尔兹曼型差分格式,首先分析了波尔兹曼方程和欧拉方程之间的关系;然后,利用一种特殊的插值技术构造了一类高分辨波尔兹曼型差分格式.最后通过数值实验验证了格式的实用性和有效性.