长江河口北槽弯道横向次生流、混合与层化   总被引：1，自引：0，他引：1  

邵聪颖  浦祥  时钟  胡国栋  王真祥 《海洋工程》2016,34(3):80-98

2013年2月25至26日(枯季/大潮)、7月23至24日(洪季/大潮)分别在长江河口北槽弯道沿着3条横向测线CS6、CSW和CS3(每条测线上有北、中、南3个站位)测得水位、流速、盐度和含沙量的时间序列资料。通过这些资料的定量计算、分析,理解弯道横向次生流、混合与层化的时、空变化和各种物理机制及其相对重要性。3条横向测线均存在横向次生流,且横向测线CS3还出现横向次生环流。枯、洪季,仅在横向测线CS6、CS3出现环状欧拉余流。枯、洪季,沿着横向测线CS3,3个站位的横向斜压梯度比离心加速度和科氏加速度都大1~2个数量级,而后两项大小接近且数量级都是10-4,罗斯贝数在1左右。这些表明:横向次生流受横向斜压梯度、离心加速度和科氏加速度共同驱动,前一项相对于后两项更加重要。沿着3条横向测线:1)枯、洪季大潮,平均势能差异分别约为54.23、66.56 J/m3,表明洪季层化强于枯季;2)枯季涨潮,平均的势能差异普遍小于落潮,而洪季涨潮,平均的势能差异普遍大于落潮,表明枯、洪季湍流混合均存在潮汐不对称性;3)枯季,由横向、纵向水深平均应变(ΦS-y、ΦS-x)引起的势能差异变化率的范围分别是-67×10~(-3)~37×10~(-3)、-7×10~(-3)~11×10~(-3)W/m~3,而洪季,相应的范围分别是-45×10~(-3)~30×10~(-3)、-14×10~(-3)~13×10~(-3)W/m~3,表明枯、洪季差异不明显,横向水深平均应变(ΦS-y)均大于纵向水深平均应变(ΦS-x),前项对水体混合与层化的影响更大;4)枯季大潮,纵向平流(ΦA-x)、横向平流(ΦA-y)、纵向水深平均应变(ΦS-x)和横向水深平均应变(ΦS-y)的潮汐平均绝对值占四项总和之比例分别为26%、33%、18%和23%,而洪季大潮,相应的值的比例分别为13%、9%、22%和56%,表明枯季,平流项(ΦA-y最大)对混合与层化的控制可能占主导地位;洪季,应变项(ΦS-y最大)可能占主导地位。无量纲数(m)被用于判别横向平流(ΦA-y)、横向水深-平均应变(ΦS-y)的相对重要性。一个概念性模式被用于显示层化与横向次生流/环流的相互关系。  相似文献   

半潜平台立柱与浮筒中部不同形式连接节点疲劳寿命分析   总被引：1，自引：0，他引：1  

傅强  王洪庆  张国栋  孙立强  李德江  李磊 《海洋工程》2016,34(4):85-92

为了研究半潜式平台的立柱与浮筒中纵舱壁连接节点出现焊缝开裂这种疲劳失效现象,利用简化疲劳方法以及三维细化有限元模型,对目前主流平台中所采用两种不同的立柱与浮筒中纵舱壁连接节点形式进行了疲劳寿命评估与分析。首先从结构刚度分配角度,平均应力效应角度分析疲劳裂纹产生的原因;然后利用疲劳分析结果评估不同连接节点对整个平台结构可靠性的影响;最后,基于结构力学性能和刚度匹配角度分析两种节点形式的优劣,确定最优节点设计方案。  相似文献   

Carbon storage in desertified lands: A case study from North China     

Feng Qi  Cheng Guodong  Endo Kunihiko 《GeoJournal》2000,51(3):181-189

Based on the organic and carbonate carbon levels of the top 1 m of soil from desertified soils of Northern People's Republic of China, climatic and vegetative cover zones have been derived for some 334000 km² of desertification-prone lands. Regional accumulations of pedogenic carbonates were examined relative to precipitation, altitude, and temperature. The largest accumulations of pedogenic carbonates were found in Calcic soils in warm, arid areas. Accumulated organic carbon predominated in soils under Betula platyphylla. In the naturally desertified lands of China, for example, the top 1.0-m soil layer contains some 7.84 Pg of organic carbon and 14.9 Pg of carbonate carbon. Total stored carbon, including carbonate carbon, is 1.8-fold more than organic carbon alone. The carbon released through land desertification in China may be an important factor affecting changes in concentrations of greenhouse gases worldwide.  相似文献   

Simulation of rainfall-runoff and watershed convergence process in the upper reaches of Heihe River Basin, July 2002     

Gao Yanhong  U Shihua  CHENG Guodong 《中国科学D辑(英文版)》2004,47(Z1)

The watershed flow concentration scheme in the distributed hydrology-soil- vegetation model (DHSVM) is coupled with the mesoscale atmospheric model MM5 version 3.5, in which the Oregen States University land surface model (OSULSM) was involved. The flood event which happened in July 2002 in the upper reaches of Heihe river basin is simulated and the surface flow convergence process is shown with this coupled model. It has been concluded that times water head reaches each place of the basin are different. Water amount at each point is split-flow proportionally as the drops in elevation between it and neighbor points. Large part of the water amount pass away in greater slope direction and small part pass away in smaller slope one.Adding of the slope convergence makes the atmospheric model redistributes the surface water laterally.  相似文献   

Ground-temperature controlling effects of duct-ventilated railway embankment in permafrost regions     

NIU Fujun  CHENG Guodong  YU Qihao 《中国科学D辑(英文版)》2004,47(Z1)

Based on observed data from field-testing embankment of the Qinghai-Tibet Railway, ground-temperature controlling effect of duct-ventilated embankment is studied in this paper.The results show that ventilation ducts can effectively cool the soils surrounding the ducts of the embankment, and the heat budget of the ambient soils in a year shows as heat release. Temperature status of the permafrost below the embankment with ducts buried in the relatively high position is similar to that of the common embankment. The permafrost processes warming all along in the two freezing-thawing cycles when the embankment was constructed. However, the temperature of the frozen soils below the embankment, in which the ducts buried in the relatively low position, rises a little in the initial stage. After that, it cools down gradually. At the same time,ventilation ducts can effectively reduce the thermal disturbance caused by the filled soils. The frozen soils below the common embankment and that with high-posited ducts absorb heat all along in the initial two cycles. While the soils below the embankment with low-posited ducts begin to release heat in the second cycle. This phenomenon proves that the ventilation embankment with low-posited ducts shows efficient temperature-controlling effect. Such embankment can actively cool the subgrade soils and therefore keeps the roadbed thermally stable.  相似文献   

Cooling effect of ballast revetment on the roadbed of Qinghai-Tibetan Railway     

Hu Zeyong  CHENG Guodong  QIAN Zeyu  WANG Jiemin  Wei Guoan  HOU Xuhong  GU Lianglei  YAN Yuping 《中国科学D辑(英文版)》2004,47(Z1)

The data obtained through the roadbed surface thermal regime experiment (ROBSTREX), which was carried out at Beiluhe test section of Qinghai-Tibetan Railway from October to December in 2002, were used to estimate the cooling effect of ballast revetment on the roadbed. The results show that both riprap rock ballast revetment and crushed stone ballast revetment can reduce the temperature of the roadbed. But the cooling effect of riprap rock ballast revetment is better than that of crushed stone ballast revetment when the temperature of roadbed is higher. The cooling effect of crushed stone ballast revetment is better than that of riprap rock ballast revetment when the temperature of the roadbed is lower, especially at deeper roadbed layers. In the frozen season, the heat release from the roadbed also shows that the cooling effect of ballast revetment on the roadbed is obvious, and the cooling effect of crushed stone-ballast revetment on the roadbed is much evident than that of riprap rock ballast revetment.  相似文献   

The application of auto-temperature-controlled ventilation embankment in Qinghai-Tibet Railway   总被引：2，自引：0，他引：2  

YU Qihao  CHENG Guodong  NIU Fujun 《中国科学D辑(英文版)》2004,47(Z1)

Auto-temperature-controlled ventilation embankment is an effective engineering measure for "cooling roadbed". Practice proves that this new method can sufficiently make use of natural cold energy. It has the advantages of higher efficiency, better cooling effect and feasibility in engineering practice, and wider application in various environment, etc. And also, it is comparatively cheap in project cost. Through practice in the field for half a year, the testing results show that, with the application of auto-temperature-controlled system, the artificial permafrost table has been raised by 65 cm. The artificial permafrost table was basically at the embankment bottom, and the action of freeze-thaw circle on engineering stability was effectively avoided. In the month with highest ground temperature, in the scope with 1-4 m in depth, including the majority of the embankment and the upper part in the original seasonal layer, the ground temperature decreased by 0.7℃. Through thermal flux calculation in the original seasonal layer, in the month with the maximum thermal flux coming into permafrost, it is found that the thermal flux reduces nearly by half. Coming into the cooling period for nearly a month, the ground temperature in entire auto-temperature-controlled embankment is close to zero, and the foundation is at negative temperature. But in a large region in the embankment and foundation the ground temperature was over 0℃ and varied from 0℃ to 0.39℃ in ordinary ventilation embankment.  相似文献   

Studies on frozen ground of China   总被引：5，自引：0，他引：5  

ZHAO Lin  CHENG Guodong  DING Yongjian 《地理学报(英文版)》2004,14(4):411-416

1ThestatusoffrozengroundinChinaBased on previous studies, Zhou and Guo (1982) summarized the distribution characteristics of permafrost in China and indicated that the permafrost area in China is about 215×104 km2, in which about 163.4×104 km2 is on the Tibetan Plateau. After mapping and zonation of frozen ground in 1983, Xu and Wang suggested that the areas of permafrost, seasonally frozen ground and temporal frozen ground in China were 206.8×104 km2, 513.7×104 km2 and 229.1×104 km2 …  相似文献   

太阳短波辐射分光谱计算模式          下载免费PDF全文

曹丽青  高国栋 《气象科学》2004,24(2):185-192

本文采用太阳短波辐射分光谱模式计算了我国太阳辐射收支各分量。模式中主要考虑及计算了大气中各种成份在不同谱区对太阳辐射的吸收和衰减作用。如水汽、均匀混和气体的红外吸收，紫外和可见光区的臭氧吸收、雷利散射及大气气溶胶的削弱作用等。给出了大气中各种成份在不同波段对太阳辐射的削弱。并且分析了我国太阳辐射收支各分量1月、7月的分布特征。模式误差在4％～10％，比较理想。为无辐射观测的高原、沙漠、海洋等地区提供了一种较好的计算方法。  相似文献   

Overbank and channelfill deposits of the modern Yellow River delta   总被引：1，自引：0，他引：1  

Andre van Gelder  Jan H. van den Berg  Guodong Cheng  Chunting Xue 《Sedimentary Geology》1994,90(3-4):293-305

The Huanghe is noted for its high transport rate of silt and clay, which may reach depth-averaged values of 200 kg m⁻³ during peak discharge. The sediment load transported through the river on entering the delta plain, amounts to 10¹² kg per year. In contrast to most other large deltas only one distributary channel is active at any one time. The high sediment load causes the rivermouth to prograde at a yearly rate of 1–4 km into the shallow (less than 20 m deep) Bohai gulf. The vertical aggradation of the channel belt and mouth bar complex is also rapid (decimetres per year on average), so that after a normal average of twelve years increasing channel instability and avulsion create the start of a new delta lobe.

A series of satellite images covering the last fifteen years has provided insight in the evolution of the river pattern as well as the progradation of the delta front. A newly developed distributary passes from a multichannel to a single, straight channel system, and ends with the formation of meanders. The protruding mature delta lobe shows a radiating pattern of crevasse channels.

Overbank/ crevasse deposits are made of vertically stacked dm-scale waning flow sequences, structurally characterized by (from bottom to top) small scour-and-fills, even (parallel) lamination, and climbing-ripple crosslamination. Accumulation rates on crevasse splays can be predicted on the basis of estimated river sediment discharge. It can be concluded that each sequence has been deposited within a few hours, and that tidal waterlevel fluctuations may have played a role in the generation of a single sequence.  相似文献