Large-Eddy Simulation Of Neutral Turbulent Flow Over Rough Sinusoidal Ridges

The requirements for a credible large-eddy simulation of neutral, turbulent flow over hills with an aerodynamically rough surface are discussed, in order to select a suitable case for simulation. As well as providing adequate resolution within the dynamically important inner region, obtaining a realistic upstream or undisturbed mean velocity profile is also of critical importance. A distributed drag canopy formulation has been introduced to the model to allow it to obtain such a profile while resolving very close to the rough surface. Simulations have then been performed of flow over ridges of varying heights. The results from the steepest case, which is just on the verge of separation, are compared with wind-tunnel observations. It is shown that the large-eddy simulation results are in much better agreement with the experimental data than are the results from a simple first-order mixing-length closure model. An encouraging lack of sensitivity of the simulation results to numerical resolution is also demonstrated.     

东亚夏季风降水和环流数值模拟对不同对流参数化方案的敏感性

A 5-level spectral AGCM (ImPKU-5LAGCM) is used to examine the sensitivity of the simulated results of the summer monsoon rainfall and circulation in East Asia to different cumulus parameterization schemes in the climatological-mean case and in the cases of weak and strong Asian summer monsoons,respectively. The results simulated with the Arakawa-Schubert＇s(hereafter A-S＇s), Kuo＇s and Manabe＇s cumulus parameterization schemes show that these simulated distributions of the summer monsoon rainfall and circulation in East Asia depend strongly on the cumulus parameterization schemes either in the climatological-mean case or in the cases of weak and strong Asian summer monsoons. From the simulated results, it might be shown that the Kuo scheme appears to be more suitable for the simulation of the summer monsoon rainfall and circulation in East Asia than the A-S scheme or the Manabe scheme, although the A-S scheme is somewhat better in the simulations of the tropical rainfall. This might be due to that the Kuo＇s cumulus parameterization scheme is able to reflect well the characteristics of rainfall cloud system in the East Asian summer monsoon region, where the rainfall system used to be a mixing of cumulus and stratus.     

NUMERICAL SIMULATION OF METHANE EMISSIONS FROM RICE PADDY FIELDS IN THE YANGTZE DELTA OF CHINA*

A numerical simulation model is presented in this paper,which comprises the processes of crop growth,soil organic carbon decomposition,and methane emissions in agroecosystems.Simulation results show that the model can simulate the main process of methane emissions well,and the correlation coefficient between the simulated values and observed data is 0.79 with 239 samples,which passed a significance test of 0.01.The average error of methane emission simulation in whole growth period is about 15%.Numerical analysis of the model indicates that the average temperature during rice growth period has much impacts on methane emissions,and the basic trend of interannual methane emissions is similar to that of average temperature.The amount of methane emissions reduces about 34.93%,when the fertilizer is used instead of manure in single rice paddy.     

1997/1998年热带太平洋海温异常的诊断分析与预报检验

通过与历史上已发生的ENSO事件的比较，对1997－1998年热带太平洋海温异常的基本特征和可能成因进行了诊断分析，发现1997／1998年E1Nino事件具有显著的异常性和独特性，不同于以往单纯的东部型或西部型E1Nino。对用一个简化海气耦合动力学模式做1998／1998年E1Nino事件的预报进行检验。结果表明该模式对这次暖事件超前0－24个月的预报技巧均在0．5以上，模式对暖事件的成熟位相及以后阶段的预报比对暖事件的开始阶段预报得好。     

应用数字摄影测量系统生成大比例尺DEM的质量分析与控制

本文结合最近完成几个项目的工作 ,介绍了应用数字摄影测量系统生成大比例尺DEM过程中的质量控制、质量分析与检测方法及经验     

Numerical modeling calculation for the spatial distribution characteristics of horizontal field transfer functions

Introduction There are two kinds of methods for the mathematic study on electro-magnetic induction in geo-field: one is analytic method, such as integral equation method; the other is numerical model-ing method, such as finite difference method and finite element method. The analytic method can only be applied to the conductor with very simple shape, such as sphere, circular cylinder, etc. With the increasing of computing speed and popularity of computer, the numerical modeling methods are use…     

LONG TERM EFFECTS OF REHABILITATION MEASURES ON BED LOAD TRANSPORT AT THE SALZACH RIVER

1 BASIC PROBLEMFlood protecton, sPreaing of settlements and occuPatin Of river valleys were maor reasons to damand lindt rivers throughout Europe in the ndd 19th century. Engineers of those days often knew very wellabout the effects of their plannings: shortening the river length would accelerat the now and thusencourage the erosion into the river's sedAnents. Two vital advanages could be obtalned from that kindof constrUction, landuse of the fOrmer flood plains on the one and increasin…     

RESUSPENSION OF FINE SEDIMENT IN RESERVOIRS - A CASE STUDY OF THE LOWER INN RIVER

1 THE LOWhR unR INNThe Inn river has its source in the alPine region of the GraubUnden canton of Switzerand. ThecatChment area of about 260(X} kIn2 includes mountains of the central Alpes up to 40(X) m. The river runs5l7 km thrOugh the countries of SwitZerand, Austria and Germany on itS way into the Danube mver. Thedischarge of the river at its mouth in the city of Passau is mainly infiuenced by the snow melt in themountainous catchment area and vches between apProx. 200 m3ls durin…     

多次透射公式的一种稳定实现措施

基于对双曲偏微分议程数值解稳定性的GKS（Gustafsson,Kreiss and Sundstrom）准则的物理解释，本文提出了在波动模拟中多次透射公式飘移失稳的一个简单措施，并用波源问题和散射问题的数值试验检验了建议的稳定措施的有效性。     

结构动力反应分析中的一种显式输入反演方法

本文简要总结，评述了结构动力反应分析中两类输入反演方法（脉动函数法和直接时域法）的优缺点，在此基础上通过应用文献[1]中提出的3阶显式方法，获得了一个关于结构输入反演问题的新解法－显式直接时域法，新方法集合了脉冲函数法和直接时域法的优点，既可按显式求解动力微方程，又适用于非线性系统的动力反演问题，最后，通过算例对该方法进行了数值验证。