鸟撞飞机风挡动态响应数值模拟方法研究现状

总结了目前用于鸟撞飞机风挡动态响应的数值模拟方法,主要有解耦解法、耦合解法和光滑质点动力学法,其中耦合解法涉及接触-碰撞耦合解法和流固耦合解法。各种方法围绕鸟体（鸟撞载荷）的模拟和风挡的模拟,部分内容针对鸟撞击发动机叶片、雷达罩和垂直尾翼等,但其方法同样适用于飞机风挡,最后指出应进一步深入研究的内容。     

Solar flux effects on equatorial ionization anomaly and total electron content over Brazil: Observational results versus IRI representations

The F layer critical frequency (foF2) as measured by Digisondes in the equatorial and low latitude locations in Brazil is analyzed to investigate the seasonal and solar flux controls of the intensity of the equatorial ionization anomaly (EIA) in the equinoctial month of March. The analysis also included the total electron content (TEC) as measured by a GPS receiver operated at the EIA crest location. The foF2 data set covered a period of large solar flux variation from 1996 to 2003, while the GPS TEC data was for a period in 2002–2003 when the solar flux parameter F10.7 underwent large variations, permitting in both cases an examination of the solar flux effects on these parameters. The seasonal variation pattern in TEC shows a maximum in equinoctial months and a minimum in June solstice, with similar variations for foF2. The solar flux dependence of the TEC is a maximum during equinoxes, especially for post-sunset TEC values at times when the latitudinal distribution is controlled by the equatorial evening plasma fountain processes. Significant variations with local time are found in the degree of solar flux dependence for both the TEC and EIA. The EIA intensity shows large dependence on F10.7 during post-sunset to midnight hours. These results are discussed in comparison with their corresponding IRI representations.     

An algorithm to separate wind tunnel background noise from turbulent boundary layer excitation

Wall pressure fluctuations generated by Turbulent Boundary Layers(TBL) provide a significant contribution in reducing the structural vibration and the aircraft cabin noise. However,it is difficult to evaluate these fluctuations accurately through a wind tunnel test because of the pollution caused by the background noise generated by the jet or the valve of the wind tunnel. In this study, a new technology named Subsection Approaching Method(SAM) is proposed to separate the wall pressure fluctuations from the background noise induced by the jet or the valve for a transonic wind tunnel test. The SAM demonstrates good performance on separating the background noise from the total pressure compared to the other method in this study. The investigation considers the effects of the sound intensity and the decay factor on the sound-source separation. The results show that the SAM can derive wall pressure fluctuations effectively even when the level of background noise is considerably higher than the level of the wall pressure fluctuations caused by the TBL. In addition, the computational precision is also analyzed based on the broad band noise tested in the wind tunnel. Two methods to improve the precision of the computation with the SAM are also suggested: decreasing the loop gain and increasing the sensors for the signal analysis.     

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。     

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.     

Recent ozone investigations over Bulgaria by remote sensing: Ground-based and satellite data

This presentation deals with the recent investigations of the dynamics of the total ozone content (TOC) and of the lower troposphere ozone over Bulgaria, South-Eastern Europe.