移动车辆荷载环境微振动的排桩隔振参数分析

为满足精密仪器振速控制要求,提出"群桩基础+隔振排桩"与空气弹簧的两级组合隔振措施.主要研究路面移动车辆荷载经过时,第一级隔振中排桩的隔振效果.实测土体小应变动力参数,通过编写车辆-路面耦合单元(VRI)子程序引入路面不平顺,并基于三维有限元法建立了道路-排桩-地基动力模型.将模拟振速经1/3倍频程滤波与实测进行对比,...     

横断山区地表真实面积与垂直投影面积差异分析 ——以雅江县为例

横断山脉地形起伏复杂,以垂直投影面积作为地表真实面积进行定量计算会产生较大误差。本文以横断山脉中部雅江县为例,基于DEM数据和地表覆盖产品数据集,利用地表粗糙度的地学意义,计算了雅江县不同土地利用类型地表真实面积,并分析了地表真实面积与垂直投影面积之间的差异。结果表明：雅江县地表面积与投影面积的差异与DEM分辨率呈正相关,与海拔呈负相关;坡度是地表面积与投影面积差异的主要影响因素,坡度越大,差异越大,差异的增长速率越大;不同土地利用类型对面积差异有不同程度的影响。     

壁面局部粗糙对大涡结构作用的非线性演化研究

在构建大涡结构理论模型的基础上,采用局部喷入和吸出的结构来模拟局部粗糙壁面诱导的感应扰动场,数值研究局部粗糙对大涡结构之间非线性作用的影响问题。数值结果表明,局部粗糙壁面诱导的感应扰动改变了原平均速度剖面的稳定性特性及感应扰动流场的三维性对激励大涡结构的快速增长起了关键性的作用。     

南京地区稻田蒸散的研究

引进半经验模式计算稻田蒸散，仅需要常规气象资料和作物的叶面积资料即可较精确地估算农田蒸散，解决了用Ｐｅｎｍａｎ－Ｍｏｎｔｅｉｔｈ方法计算误差偏高以及需要风速梯度观测等在实际应用中存在的困难。通过对模式进行参数的敏感性分析，证实了模式的可靠性和可行性。分析稻田蒸散发现水稻一生有两个耗水高峰：拔节期和抽穗开花期，此时的气象条件最有利于水稻蒸散的进行。     

The bulk aerodynamic formulation over heterogeneous surfaces

This interpretative literature survey examines problems with application of the bulk aerodynamic method to spatially averaged fluxes over heterogeneous surfaces. This task is approached by tying together concepts from a diverse range of recent studies on subgrid parameterization, the roughness sublayer, the roll of large inactive boundary-layer eddies, internal boundary-layer growth, the equilibrium sublayer, footprint theory and the blending height. Although these concepts are not completely compatible, qualitative scaling arguments based on these concepts lead to a tentative unified picture of the qualitative influence of surface heterogeneity for a wide spectrum of spatial scales.Generalization of the velocity scale is considered to account for nonvanishing heat and moisture fluxes in the limit of vanishing time-averaged wind speed and to account for the influence of subgrid mesoscale motions on the grid-averaged turbulent flux. The bulk aerodynamic relationship for the heat flux usually employs the surface radiation temperature or, equivalently, the temperature from the modelled surface energy budget. The corresponding thermal roughness length is quite variable and its dependence on available parameters is predictable only in special cases.An effective transfer coefficient to relate the spatially averaged surface fluxes to spatially averaged air-ground differences of temperature and other scalars can be most clearly defined when the blending height occurs below the reference level (observational level or first model level). This condition is satisfied only for surface heterogeneity occurring over horizontal scales up to a few times the boundary-layer depth, depending on the stability and height of the reference level. For surface heterogeneity on larger scales (small mesoscale), an effective transfer coefficient for the spatially averaged flow must be defined, for which predictive schemes are unavailable. For surface variations on large mesoscales, homogeneous subareas may be maintained where traditional similarity theory is locally applicable. Surface variations on these scales may generate thermally-driven mesoscale motions.     

The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer

Full-scale observations from two urban sites in Basel, Switzerland were analysed to identify the magnitude of different processes that create, relocate, and dissipate turbulent kinetic energy (TKE) in the urban atmosphere. Two towers equipped with a profile of six ultrasonic anemometers each sampled the flow in the urban roughness sublayer, i.e. from street canyon base up to roughly 2.5 times the mean building height. This observational study suggests a conceptual division of the urban roughness sublayer into three layers: (1) the layer above the highest roofs, where local buoyancy production and local shear production of TKE are counterbalanced by local viscous dissipation rate and scaled turbulence statistics are close to to surface-layer values; (2) the layer around mean building height with a distinct inflexional mean wind profile, a strong shear and wake production of TKE, a more efficient turbulent exchange of momentum, and a notable export of TKE by transport processes; (3) the lower street canyon with imported TKE by transport processes and negligible local production. Averaged integral velocity variances vary significantly with height in the urban roughness sublayer and reflect the driving processes that create or relocate TKE at a particular height. The observed profiles of the terms of the TKE budget and the velocity variances show many similarities to observations within and above vegetation canopies.     

Characteristics of Momentum and Heat Transfer over Semiarid Grasslands with Different Grazing Intensities in Inner Mongolia, China

The drag coefficient (C d) and heat transfer coefficient (C h) with the bulk transfer scheme are usually used to calculate the momentum and heat fluxes in meteorological models.The aerodynamic roughness length (z 0m) and thermal roughness length (z 0h) are two crucial parameters for bulk transfer equations.To improve the meteorological models,the seasonal and interannual variations of z 0m,z 0h,coefficient kB 1,C d,and C h were investigated based on eddy covariance data over different grazed semiarid grasslands of Inner Mongolia during the growing seasons (May to September) from 2005 to 2008.For an ungrazed Leymus chinensis grassland (ungrazed since 1979),z 0m and z 0h had significant seasonal and interannual variations.z 0m was affected by the amount and distribution of rainfall.kB 1 exhibited a relatively negative variation compared with z 0h,which indicates that the seasonal variation of z 0h cannot be described by kB 1.To parameterize z 0m and z 0h,the linear regressions between ln(z 0m),ln(z 0h),and the leaf area index (LAI) were performed with R 2 =0.71 and 0.83.The monthly average kB 1 was found to decrease linearly with LAI.The four-year averaged values of C d and C h were 4.5×10 3 and 3.9×10 3,respectively.The monthly average C d only varied by 8% while the variation of C h was 18%,which reflects the different impacts of dead vegetation on momentum and heat transfer at this natural grassland.Moreover,with the removal of vegetation cover,grazing intensities reduced z 0m,z 0h,C d,and C h.     

近海层大气湍流通量系数研究

根据１９９４年９月１８～３０日南沙群岛海域渚碧礁的近海面大气湍流观测实验资料,分别计算了该海域光滑海面和粗糙海面上的空气动力粗糙度（ｚ０ ）、中性曳力系数（ Ｃ Ｄ Ｎ）。利用 Ｂｕｔｓａｅｒｔ 的假定,推导了求取标量粗糙度（ｚ Ｔ、ｚ Ｑ）、整体输送系数（感热交换系数 Ｃ Ｈ Ｎ、水汽交换系数 Ｃ Ｅ Ｎ ）的一组公式。在此基础上,分别计算和分析了该海域光滑海面和粗糙海面上空气动力粗糙度（ｚ０ ）、标量粗糙度（ｚ Ｔ、ｚ Ｑ ）、中性曳力系数（ Ｃ Ｄ Ｎ）、整体输送系数（感热交换系数 Ｃ Ｈ Ｎ、水汽交换系数 Ｃ Ｅ Ｎ）及其关于水平风速分量的分布,并得到了一些有益的结论。     

二氧化硫干沉降的测量

通过在成都市郊对二氧化硫气体浓度和气象要素进行同步梯度观测,得到二氧化硫的干沉降速度.总结了影响二氧化硫干沉降速度的主要因子及日变化规律,发现其干沉降速度白天大于夜间,并在白天午后15时前后出现极大值,夜间2时前后出现极小值,平均沉降速度为1—1.5cm/s,且随稳定度的增加干沉降速度减小.