改性SST固化剂在高等级公路工程中的应用研究

介绍了国内外高等级公路工程中应用ＳＳＴ固化剂施工的基本情况，着重介绍自行开发的改性ＳＳＴ固化剂的改性技术、机理分析、工艺要领与工程质量数据，并作出了技术经济评估。     

RANS and LES computations of the tip-leakage vortex for different gap widths

In hydraulic turbines, the tip-leakage vortex is responsible for flow instabilities and for promoting erosion due to cavitation. To better understand the tip vortex flow, Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) computations are carried out to simulate the flow around a NACA0009 blade including the gap between the tip and the wall. The main focus of the study is to understand the influence of the gap width on the development of the tip vortex, as for instance its trajectory. The RANS computations are performed using the open source solver OpenFOAM 2.1.0, two incidences and five gaps are considered. The LESs are achieved using the YALES2 solver for one incidence and two gaps.

The validation of the results is performed by comparisons with experimental data available downstream the trailing edge. The position of the vortex core, the mean velocity and the mean axial vorticity fields are compared at three different downstream locations. The results show that the mean behaviour of the tip vortex is well captured by the RANS and LES computations compared to the experiment. The LES results are also analysed to bring out the influence of the gap width on the development of the tip-leakage vortex. Finally, a law that matches the vortex trajectory from the leading edge to the mid-chord is proposed. Such a law can be helpful to determine, in case of cavitation, if the tip vortex will interact with the walls and cause erosion.     

无限展长后掠翼边界层定常横流不稳定转捩分析

采用γ-Re_θt横流转捩拓展模型对NLF （2）-0415无限展长后掠机翼进行数值模拟,重点分析来流雷诺数、机翼表面粗糙度及后掠角对边界层横流不稳定性的影响.研究发现γ-Re_θt横流转捩拓展模型能够准确预测边界层定常横流不稳定转捩,计算结果与试验数据吻合较好.结果表明来流雷诺数越大、机翼表面越粗糙,横流转捩位置越靠前;随着机翼后掠角的增加,转捩位置先前移随后逐渐靠后.     

两种湍流模型时域颤振计算方法研究

采用时域计算分析方法进行了机翼跨音速颤振特性研究。在结构运动网格的基础上,采用格点格式有限体积方法进行空间离散和双时间全隐式方法进行时间推进求解雷诺平均N-S方程。针对流动粘性分别应用了SST湍流模型和SSG雷诺应力模型,通过对跨音速标模算例AGARD445.6机翼的计算结果与实验值的对比分析,其中应用SST湍流模型得到的颤振速度与实验值最为接近,特别是在跨音速段平均相对误差在3%以内;并且计算结果整体上反映了跨音速颤振"凹坑"物理特性,验证了方法的有效性。     

基于转捩SST模型凸起圆柱绕流数值研究

为了研究局部凸起对边界层转捩的影响,采用转捩SST模型分别对亚临界、临界和超临界状态下带突起的圆柱绕流问题进行了数值模拟,分析了不同Reynolds数下带突起的圆柱绕流问题的近壁面流动特征以及表面时均压力与摩擦力系数的分布和凸起对圆柱表面流动分离以及转捩的影响,对比了有无凸起两侧圆柱表面时均压力、摩擦力系数的不同. 结果表明:当来流Reynolds数处于临界区时,气流在圆柱上表面凸起处形成了3个反向旋转的漩涡,之后随着θ的增大,发生了流动分离和流动转捩现象;对于不同Reynolds数下的来流,圆柱上表面的凸起可以使气流发生转捩的位置提前;圆柱上表面的凸起使流速增大、压强降低,从而导致圆柱产生升力,随着来流Reynolds数的增大,其升力逐渐变大.      

Quantitative Analysis of Planktonic Foraminifera in Surface Sediments From the South China Sea

Q-mode factor analysis was applied to 99 surface samples from the South China Sea to define four planktonic foraminiferal assemblages: tropical-subtropical assemblage, high-salinity assemblage, transitional assemblage and dissolution resistant assemblage. The tropical-subtropical assemblage is a dominant assemblage. The variation of the planktonic foraminifera of this assemblage reflects the changes of tropical surface water from the west Pacific to South China Sea. These four assemblages reveal that different planktonic foraminiferal assemblages are controlled by different factors in the South China Sea, such as tropical-subtropical assemblage controlled by sea surface temperature (SST), high-sallnity assemblage mainly by salinity besides SST, transitional assemblage by SST and dissolution resistant assemblage by water depth.     

THE MULTIPLE EQUILIBRIA IN THE COUPLED ATMOSPHERE-OCEAN SYSTEM

In this paper, a topography forced quasi-geostrophic baroclinic model and an SST (sea surface temperature) equation are used to set up a simple coupled atmosphere-ocean model The large-scale ocean current is nearly the Sverdrup flow. Two basic processes are considered in this system, i. e. the SST as a thermal forcing drives the atmospheric circulation and the ocean current produced by the wind redistributes the SST. Highly truncating and multiple scale method are used to simplify the model and obtain a low dimensional dynamic system. In this part, the qualitative vector in the phase space of the system is analysed and two stable equilibria are obtained. These two kinds of equailibria may be used to explain some features of the long-range anomalies of circulation.     

基于CUDA并行的全球海洋表面温度场等值线提取算法研究

在分析GPU并行架构和CUDA灵活可编程性基础上,提出了一种基于区间块搜索的等值线并行提取方法,可应用于全球海洋表面温度格网数据的分析.算法有效减少了等值线追踪过程中重复性的格网遍历及不必要的格网搜索.最后,实验采用了不同规模的海表温度场格网数据进行等值线的提取并比较串并行耗时,结果表明:(1)算法能实现全球海洋表面温度等值线的有效提取并提高其效率,尤其对于大规模格网数据;(2)基于所有实验数据,格网规模大于720×1 440时,相较于串行过程GPU执行体现了其效率上的优势,GPU与CPU串行耗时的加速比最大可达3.124.     

Detection of Sea Surface Temperature (SST) and Salinity Using Thermal Infrared Data of AVHRR and MODIS in the Gulf of Bohai Sea of China

This paper presents the detection of sea surface temperature (SST) and salinity in the Gulf of Bohai Sea of China using thermal infrared (TIR) data of Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS). Both AVHRR and MODIS imageries are evaluated as main data sources for monitoring SST as a measure of upwelling's dynamic. The relationship between SST and salinity in the area is also discussed during 1997-2000 derived from AVHRR data and then examined using MODIS data of 2000. The obtained results indicated that both AVHRR and MODIS are useful to detect SST and salinity in the study area.     

Transition Modelling for General Purpose CFD Codes

The paper addresses modelling concepts based on the RANS equations for laminar-turbulent transition prediction in general-purpose CFD codes. Available models are reviewed, with emphasis on their compatibility with modern CFD methods. Requirements for engineering transition models suitable for industrial CFD codes are specified. A new concept for transition modeling is introduced. It is based on the combination of experimental correlations with locally formulated transport equations. The concept is termed LCTM – Local Correlation-based Transition Model. An LCTM model, which satisfies most of the specified requirements is described, including results for a variety of different complex applications. An incremental approach was used to validate the model, first on 2D flat plates and airfoils and then on to progressively more complicated test cases such as a three-element flap, a 3D transonic wing and a full helicopter configuration. In all cases good agreement with the available experimental data was observed. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of transition correlations with general purpose CFD codes. There is a strong potential that the model will allow the 1st order effects of transition to be included in everyday industrial CFD simulations.