可压缩球涡和平面激波相互作用的数值研究

行进了可压缩球涡和平面激波相互作用的数值研究。一方面，用非定常Euler方程数值模拟了一种可压缩球涡的自身演化，同时，利用Rankine－Hugoniot关系，在流场中嵌入运动激波，求解了激波－球涡相干的流动过程。通过改变激波强度Ms和旋涡强度Mv，研究了激波－球涡相互作用的参数依赖关系。结果表明：对于不同的参数范围，波－涡相干的流场结构也出现几种不同的形式。其中，强激波和强涡球的相互作用会导致激波分叉和旋涡强烈畸变等复杂流动现象。

Beltrami流动的球涡解的张量表示及其对称性分析

讨论了一类Beltrami流动的 n阶球涡 (非轴对称及轴对称 )的张量表示及由此引出的对其的分类和对称性的研究 ,还进一步地讨论了单个此类非轴对称n阶球涡解的混沌现象 ;从另一侧面说明了非轴对称Beltrami流动的球涡解的复杂性及多样性 。

2006-2015全球涡轴式发动机直升机和旋翼机市场十年预测报告

2006年初，罗罗公司与蒂尔集团合作在达拉斯公布了每年一度的全球军／民用涡轴式发动机直升机和旋翼无人机市场十年（2006-2015）预测报告。

流体动力学方程的三维旋涡解的可叠加性

给出了流体动力学方程的轴对称流动的一类精确解 ,讨论了一些例子并综述了目前已知的基本涡元精确解· 发现三维空间内的某些旋涡解可以叠加成仍然满足非线性方程的新的精确解· 由此可以用来分析旋涡的产生。

声激励对圆射流流场结构控制的大涡模拟

为研究声激励对圆射流流场结构的控制作用,采用大涡模拟方法计算相锁定全局声激励下的圆射流(Re=2 020)流场.计算得出的未加激励时射流的优势频率与实验符合得很好.从多角度描述声激励对射流速度场和涡量场的影响,分析流场对声激励响应的频率选择特性.通过速度场的平均值、均方根值,概率密度函数,偏度,峰度,以及动量厚度的分布,显示声激励引起速度场和混合特性的改变.涡量和Q准则揭示流场拟序结构的演化,发现激励控制流场的主导涡结构是希尔球涡.研究表明,声激励是流场控制非常准确和有效的手段,当激励频率在优势频率附近时影响尤其明显,很小的能量输入便可以引起流场结构的显著改变.

球凸对螺旋半圆管内流体流动及传热的影响

采用RNGk-ε湍流模型数值研究了球凸涡发生器对螺旋半圆管夹套内流体湍流流动及换热的影响,分析了泊肃叶数P0、努塞尔数Nu及综合性能因子PEC随雷诺数Re的变化关系,并与光滑螺旋夹套进行对比,结果表明:湍流状态下,球凸涡发生器可以提高螺旋半圆管的努塞尔数,但其综合性能评价因子PEC值小于1,说明阻力系数的增值大于传热系数的增值。

广西前汛期区域性暴雨落区判据的若干方法

首先引进了螺旋度概念及计算方法，并计算两个强对流天气个例的螺旋度值，认为螺旋度可作为用于预报强对流天气的一个参数，其次利用吴国雄提出的P坐标的倾斜涡度发展理论分析方法，讨论前汛期锋面暴雨落区的预报可行性。

中尺度暴雨生成的机制分析

对一次引起广西暴雨增幅的天气过程进行天气形势、物理量的诊断分析，并在此基础上重点讨论湿球位涡与暴雨的关系，得出条件性对称不稳定是暴雨产生的机制之一。

农村饮用水供给一体化样机开发试验研究

以混凝、沉淀、过滤为主要工艺开发了一种农村饮用水供给一体化样机,以聚合氯化铝为混凝剂,考察了进水流量和加药量对处理效果的影响,其出水水质(以浊度为主要分析指标)可满足国家规定的要求,且该装置的建造费用较传统的工艺组合低,吨水处理费用只有0.31元。该装置采用的工艺可以用于以地表水为水源的农村地区供水处理,对于与本试验所采用水源水质差别较大的地区或以地下水为水源的地区的给水处理,尚需做相关的适应性研究。

Seasonality of the Lagged Relationship between ENSO and the Northern Hemispheric Polar Vortex Variability

<Abstract>This paper reports the seasonal feature of the relationship between ENSO and the stratospheric Polar Vortex Oscillation (PVO) variability in the Northern Hemisphere.It is shown that the lagged ENSO-PVO coupling relationship exhibits distinct seasonal feature,due to the strong seasonality of PVO and ENSO.Specifically,the PVO variability not only during winter,but also in autumn and spring months,is significantly correlated with ENSO anomalies leading by seasons;however,no significant effect of ENSO is found on the PVO variability in winter months of November and February.Although a significant ENSO effect is primarily observed when ENSO leads PVO by about one year,a significant correlation is also found between PVO in the following spring months (M +1 A +1) and ENSO anomalies in the previous autumn (A-1 S-1 O- 1 N -1) when ENSO anomalies lead by about 18 months.The significant correlation between PVO in various seasons and the corresponding ENSO anomalies leading by seasons could be explicitly verified in most of the individual years,confirming that the lagged ENSO effect can largely modulate the seasonal timescale variability of PVO.Moreover,the composite spatial patterns of the zonal-mean temperature anomalies further show that the ENSO effect on the PVO in various seasons is related to the interannual variability of the seasonal timescale PVO events.

Formation Mechanism and Characteristics Research of Ball Lightning Based on Vortex Model

The strange characteristics of ball lightning are considered as a question hard to explain. In order to solve the problem, in this paper a complete model of plasma vortex is presented for the ball lightning. By ideal MHD equations, through imposing disturbance to plasma column, the possibility of sausage and kink instability of the lightning channel is analyzed from the perspective the minimum potential energy. The conclusion is that the kink instability （m = 1） is most prone to occur. And when instability occurs, because of the difference of the magnetic field in the twisted area, the magnetic pressure makes the trend further and therefore forming the plasma vortex that may eventually turn into ball lightning if the energy of the vortex is large enough. The existence of the vortex makes ball lightning have a short period of time stability. By the proposed model, the ball lightning features that are hard to understand in the past are explained. In this paper, the reason for bead lightning is also explained from the perspective of the sausage instability.

Sensitivity of Near Real-time MODIS Gross Primary Productivity in Terrestrial Forests Based on Eddy Covariance Measurements

As an important product of Moderate Resolution Imaging Spectroradiometer(MODIS), MOD17A2 provides dramatic improvements in our ability to accurately and continuously monitor global terrestrial primary production, which is also significant in effort to advance scientific research and eco-environmental management. Over the past decades, forests have moderated climate change by sequestrating about one-quarter of the carbon emitted by human activities through fossil fuels burning and land use/land cover change. Thus, the carbon uptake by forests reduces the rate at which carbon accumulates in the atmosphere. However, the sensitivity of near real-time MODIS gross primary productivity(GPP) product is directly constrained by uncertainties in the modeling process, especially in complicated forest ecosystems. Although there have been plenty of studies to verify MODIS GPP with ground-based measurements using the eddy covariance(EC) technique, few have comprehensively validated the performance of MODIS estimates(Collection 5) across diverse forest types. Therefore, the present study examined the degree of correspondence between MODIS-derived GPP and EC-measured GPP at seasonal and interannual time scales for the main forest ecosystems, including evergreen broadleaf forest(EBF), evergreen needleleaf forest(ENF), deciduous broadleaf forest(DBF), and mixed forest(MF) relying on 16 flux towers with a total of 68 site-year datasets. Overall, site-specific evaluation of multi-year mean annual GPP estimates indicates that the current MOD17A2 product works highly effectively for MF and DBF, moderately effectively for ENF, and ineffectively for EBF. Except for tropical forest, MODIS estimates could capture the broad trends of GPP at 8-day time scale for all other sites surveyed. On the annual time scale, the best performance was observed in MF, followed by ENF, DBF, and EBF. Trend analyses also revealed the poor performance of MODIS GPP product in EBF and DBF. Thus, improvements in the sensitivity of MOD17A2 to forest productivity require continued efforts.

Northern Hemisphere Stratospheric Polar Vortex Extremes in February under the Control of Downward Wave Flux in the Lower Stratosphere

Using ECWMF ERA-40 and Interim reanalysis data, the planetary wave fluxes associated with the February extreme stratospheric polar vortex were studied. Using the three-dimensional Eliassen-Palm (EP) flux as a measure of the wave activity propagation, the authors show that the unusual warm years in the Arctic feature an anomalous weak stratosphere-troposphere coupling and weak downward wave flux at the lower stratosphere, especially over the North America and North Atlantic (NANA) region. The extremely cold years are characterized by strong stratosphere-troposphere coupling and strong downward wave flux in this region. The refractive index is used to examine the conception of planetary wave reflection, which shows a large refractive index (low reflection) for the extremely warm years and a small refractive index (high reflection) for the extremely cold years. This study reveals the importance of the downward planetary wave propagation from the stratosphere to the troposphere for explaining the unusual state of the stratospheric polar vortex in February.

Effects of Bulbous Bow on Cross-Flow Vortex Structures Around a Streamlined Submersible Body at Intermediate Pitch Maneuver： A Numerical Investigation

A flow field around a streamlined body at an intermediate angle of incidence is dominated by cross-flow separation and vortical flow fields. The separated flow leads to a pair of vortices on the leeside of the body; therefore, it is essential to accurately determine this pair and estimate its size and location. This study utilizes the element-based finite volume method based on RANS equations to compute a 3D axisymmetric flow around a SUBOFF bare submarined hull. Cross-flow vortex structures are then numerically simulated and compared for a submarine with SUBOFF and DRDC STR bows. Computed results of pressure and shear stress distribution on the hull surface and the strength and locations of the vortex structures are presented at an intermediate incidence angle of 20°. A wind tunnel experiment is also conducted to experimentally visualize the vortex structures and measure their core locations. These experimental results are compared with the numerical data, and a good agreement is found.

涡桨支线飞机市场观察与展望

目前全球涡桨支线飞机占支线飞机总数量的11％，呈现出ATR和庞巴迪两强争霸，中国航空工业奋起直追的局面。涡桨飞机市场区域性差异明显。“新舟”系列定位于南亚、非洲、拉美和独联体国家等地区，这样可以与其他制造商形成错位竞争并占有不同的细分市场。

三次多项式温度分布液相模型在液滴蒸发中的应用

三次多项式温度分布模型反映了液滴内部基于希尔球涡的实际流动,可以较为准确地预测单个液滴蒸发。鉴于三次多项式温度分布模型在预测单个液滴蒸发的准确高效性,本文以n-Decane油滴蒸发为例,采用三次多项式模型研究了通过改变初温和初始气流速度来改变初始雷诺数对液滴蒸发的影响,结果表明通过改变气流速度来改变雷诺数的情况,不同雷诺数下液滴蒸发率与内部温度分布存在较大差异;以n-Decane,n-Heptane和n-Dodecane三种不同黏度的油滴蒸发为例,对比了液滴黏度对蒸发的影响,发现不同黏度液滴的蒸发率与内部温度分布差异较大,黏度越小,蒸发率越快;在液滴蒸发的初始阶段,内部温度梯度较大。

Dynamic mode decomposition of hairpin vortices generated by a hemisphere protuberance

We present dynamic mode decomposition (DMD) for studying the hairpin vortices generated by hemisphere protuberance measured by two-dimensional (2D) time-resolved (TR) particle image velocimetry (PIV) in a water channel. The hairpins dynamic information is extracted by identifying their dominant frequencies and associated spatial structures. For this quasi-periodic data system, the resulting main Dynamic modes illustrate the different spatial structures associated with the wake vortex region and the near-wall region. By comparisons with proper orthogonal decomposition (POD), it can be concluded that the dynamic mode concentrates on a certain frequency component more effectively than the mode determined by POD. During the analysis, DMD has proven itself a robust and reliable algorithm to extract spatial-temporal coherent structures.

A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes

The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee''s total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The Mach number Ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tubes, the peak pressure produced by the twin impulse waves and its location strongly depend upon the distance between two-parallel tubes, L/d and the incident shock Mach number, Ms. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

The evolution and instability of wake structure around an impulsively stopped sphere with a streamwise magnetic field for 600≤Re≤1400

The evolution of wake structure in a flow around an impulsively stopped sphere in an incompressible viscous fluid is investigated under the influence of a streamwise magnetic field at moderate Reynolds numbers.The research parameter range is 600≤Re≤1400 and 0≤N≤10,where Re and N are the Reynolds number and the interaction parameter,respectively.A vortex ring system is developed,which contains the primary and secondary vortex rings after stopping the sphere.The flow will keep axisymmetric before stopping the sphere for the purpose to investigate the instability of shedding vortex rings.Without the magnetic field,an azimuthal instability will develop on the secondary vortex ring when the Reynolds number is large enough,e.g.,Re=1200.It is caused by the centrifugal movement of the secondary vortex ring and this instability can be suppressed by the streamwise magnetic field.Furthermore,an obvious oscillation caused by the motion of the primary vortex ring on the drag force is found after stopping the sphere.The amplitude of such oscillation increases with enlarging the Reynolds number but decreases with enlarging the magnetic field intensity.

Partial and Spectral-Viscosity Models for Geophysical Flows

Two models based on the hydrostatic primitive equations are proposed.The first model is the primitive equations with partial viscosity only,and is oriented towards large-scale wave structures in the ocean and atmosphere.The second model is the viscous primitive equations with spectral eddy viscosity,and is oriented towards turbulent geophysical flows.For both models,the existence and uniqueness of global strong solutions are established.For the second model,the convergence of the solutions to the solutions of the classical primitive equations as eddy viscosity parameters tend to zero is also established.