Characterization of hydraulic suitability of Chinese sturgeon (Acipenser sinensis) spawning habitat in the Yangtze River   总被引：1，自引：0，他引：1  

Yuankun Wang  Ziqiang Xia  Dong Wang 《水文研究》2012,26(23):3489-3498

Hydrodynamic flow fields affect the ecological processes such as the water diversity and the distribution of organisms. Understanding the hydrodynamic and ecological processes is critical for the restoration and protection of especially fragile ecological habitats in river systems. This study uses turbulent flow to characterize the ecological behaviour of Chinese Sturgeon (Acipenser sinensis) in the Yangtze River. The Delft3D‐Flow model, which is first validated with field‐measured data, is used to simulate the flow field within spawning habitats of Chinese Sturgeon, downstream of Gezhouba Dam. The model‐simulated turbulent kinetic energy (TKE) and its distribution pattern are then used to characterize the hydraulic environment of the fish's spawning habitat. For the spawning habitat, downstream of Gezhouba Dam, the lower limit of TKE for the Chinese Sturgeon egg mass field is 0.025 m²/s², which occurs at a velocity less than 1.7 m/s. Chinese Sturgeon prefers habitats with TKE range of 0.010 ~ 0.015 m²/s² for resting. This suggests that discharge regimes provide the basis for ecological regulation of the Three Gorges Reservoir and the scientific reference for river management. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

“门”地貌单元的能量耗散和过程机制     

倪培桐  吴超羽  刘欢 《热带海洋学报》2012,(2):34-40

基岩岛屿组成的"门"地貌单元是珠江河口区别于世界其他河口的重要地貌特征之一。文章基于重整化群k-ε湍流模型(RNG k-ε)的FLOW3D流体计算模型研究了"门"地貌单元的时均动力结构及湍流能耗特性。"门"地形致动力结构伴随不同类型能耗区。根据能耗空间分布特性可分为核心区(A1区)、混合区(A2区)、上游区(A3区)、下游区(A4区)。"门"地形作用下,不同分区的动力结构、湍流特性、能量转化、能量耗散特征及其驱动机制不同。  相似文献   

磨刀门河口环流与咸淡水混合层化机制   总被引：1，自引：0，他引：1       下载免费PDF全文

吕紫君  冯佳佳  郜新宇  汪玉平  张梦茹  孔俊 《水科学进展》2017,28(6):908-921

为研究磨刀门盐水混合层化特征,基于SCHISM模型,建立了三维盐度数值模型,根据实测资料对其进行验证。结合水体势能异常理论,对枯季磨刀门河口混合层化的时空变化特征及深槽与浅滩的层化机制差异进行分析。结果表明:磨刀门河口小潮时水体层化最强,中潮时水体层化最弱,且拦门沙至挂定角段水体层化始终较强。磨刀门深槽水体层化主要受纵向平流、纵向水深平均应变和垂向混合影响,而浅滩水体层化则受横向平流、横向水深平均应变和垂向混合影响;磨刀门河口表、底层水体湍动能耗散率较高,而中间水层存在低耗散区,且涨潮时湍动能耗散率比落潮时大。  相似文献   

Turbulent intensity and its similarity function over an Inner Mongolian grassland during spring     

YUE Ping      NIU ShengJie  HU YinQiao & ZHANG Qiang Key Laboratory of Arid Climate Change  Reducing Disaster of Gansu Province  Key Laboratory of Arid Climate Change  Reducing Disaster of CMA 《中国科学:地球科学(英文版)》2010,(5)

Macroscopic reason for the development of turbulences in fluid is the conjunction action of velocity and temperature shears. We use the 2008 spring flux observations in the surface layer over Inner Mongolian grassland, obtain the similarity functions of turbulent intensity under different stratification stability conditions, and calculate the clear day turbulent intensity in the spring, which is then analyzed and compared with the observed values of turbulent intensity. The results show that in the Inner Mo...  相似文献   

Running safety analysis of a train on the Tsing Ma Bridge under turbulent winds     

Weiwei Guo  He Xia  Youlin Xu 《地震工程与工程振动(英文版)》2010,9(3):307-318

The dynamic responses of the Tsing Ma suspension bridge and the running behaviors of trains on the bridge under turbulent wind actions are analyzed by a three-dimensional wind-train-bridge interaction model. This model consists of a spatial finite element bridge model, a train model composed of eight 4-axle identical coaches of 27 degrees-of-freedom, and a turbulent wind model. The fluctuating wind forces, including the buffeting forces and the self-excited forces, act on the bridge only, since the train runs inside the bridge deck. The dynamic responses of the bridge are calculated and some results are compared with data measured from Typhoon York. The runnability of the train passing through the Tsing Ma suspension bridge at different speeds is researched under turbulent winds with different wind velocities. Then, the threshold curve of wind velocity for ensuring the running safety of the train in the bridge deck is proposed, from which the allowable train speed at different wind velocities can be determined. The numerical results show that rail traffic on the Tsing Ma suspension bridge should be closed as the mean wind velocity reaches 30 m/s.  相似文献   

塔克拉玛干沙漠腹地地表辐射与能量平衡   总被引：4，自引：4，他引：0  

杨帆  王顺胜  何清  霍文  杨兴华  郑新倩  王毅  蔡文军  买买提艾力&#  买买提依明 《中国沙漠》2016,36(5):1408-1418

利用2013年塔克拉玛干沙漠塔中流动沙面地表辐射、土壤热通量、土壤温湿度和湍流通量观测资料,分析了沙漠腹地地表辐射和能量收支特征及闭合状况。结果表明：除潜热通量外,其余地表辐射各分量和能量平衡分量的月平均日变化结果整体均表现为标准的单峰型日循环形态,其中R_s↓与R_s↑变化同步,R_l↑、R_l↓滞后R_s↓0.5 ~ 1 h。各分量均表现出夏季高、春秋季次之、冬季低的季节波动性。干旱和极低的植被覆盖造成沙漠腹地全年潜热通量始终较为微弱,约占净辐射的2.8%,感热通量成为能量的主要消耗形式,约占净辐射的49%。偶尔的降水会刺激潜热通量突然增加。地表反照率相对较高且稳定,日变化呈早晚大、正午小的“U”型趋势,并具有明显的冬季高、夏季低的季节波动性,年均值0.28,月均值0.25~0.32。能量残差各月的日变化也均呈单峰曲线,日出后和日落前能量闭合程度最佳,并出现过闭合现象,全年夏季小,春秋季次之,冬季较大,月平均日峰值5.1~99.9 W·m^-2。土壤表层热储存是影响该地区能量平衡的重要因子之一,考虑表层土壤热存储后,地表能量闭合率达75.3%,能量闭合率夏季 > 春季 > 秋季 > 冬季,白天相比夜间有大幅提升。  相似文献   

塔里木盆地南缘策勒典型下垫面水的湍流特征     

苏永亮  穆桂金  潘燕芳  李开封  桂东伟 《干旱区地理》2011,34(3):458-463

基于2010年3月28日天气过程在策勒地区实测风速数据,分析戈壁、绿洲农田、灌木林三种典型下垫面3 m高度水平风速的最大脉动风速、湍流强度、阵风因子等湍流特征,结果显示:(1)近地层湍流在时间序列上具有多尺度复杂性,湍流强度、阵风因子均随分析时距增大呈对数增长;(2)以10 min为分析时距获得的各项参数都显示绿洲植被...  相似文献   

Simulation of the ocean surface mixed layer under the wave breaking   总被引：6，自引：4，他引：2  

SUN Qun  SONG Jinbao  GUAN Changlong 《海洋学报(英文版)》2005,24(3):9-15

A one-dimensional mixed-layer model, including a Mellor-Yamada level 2.5 turbulence closure scheme, was implemented to investigate the dynamical and thermal structures of the ocean surface mixed layer in the northern South China Sea. The turbulent kinetic energy released through wave breaking was incorporated into the model as a source of energy at the ocean surface, and the influence of the breaking waves on the mixed layer was studied. The numerical simulations show that the simulated SST is overestimated in summer without the breaking waves. However, the cooler SST is simulated when the effect of the breaking waves is considered, the corresponding discrepancy with the observed data decreases up to 20% and the MLD calculated averagely deepens 3.8 m. Owing to the wave-enhanced turbulence mixing in the summertime, the stratification at the bottom of the mixed layer was modified and the temperature gradient spread throughout the whole thermocline compared with the concentrated distribution without wave breaking.  相似文献   

STUDY ON CLIMATIC FEATURES OF SURFACE TURBULENT HEAT EXCHANGE COEFFICIENTS AND SURFACE THERMAL SOURCES OVER THE QINGHAI-XIZANG PLATEAU   总被引：1，自引：0，他引：1       下载免费PDF全文

ZHAO Ping  CHEN Longxun 《Acta Meteorologica Sinica》2000,14(1):13-29

Using monthly mean of surface turbulent heat exchange coefficients calculated based on datafrom four automatic weather stations(AWS)for thermal equilibrium observation in July 1993—September 1996 and of surface conventional measurements,an empirical expression is establishedfor such coefficients.With the expression,the heat exchange coefficients and the components ofsurface thermal source are computed in terms of 1961—1990 monthly mean conventional data from148 stations over the Qinghai-Xizang(Tibetan)Plateau(QXP)and its adjoining areas,and the1961—1990 climatic means are examined.Evidence suggests that the empirical expression is capable of showing the variation of the heatexchange coefficient in a climatic context.The monthly variation of the coefficients averaged overthe QXP is in a range of 4×10~(-3)-5×10~(-3).The wintertime values are bigger in the mountainsthan in the valleys and reversal in summer.Surface effective radiation and sensible heat are thedominant factors of surface total heat.In spring surface sensible heat is enhanced quickly,resulting in two innegligible regions of sensible heat,one in the west QXP and the other innorthern Tibet.with their maximums emerging in different months.In spring and summersensible heat and surface effective radiation are higher in the west than in the east.The effectiveradiation peaks for the east in October—December and the whole QXP and in June and October forthe west.The surface total heat of the plateau maximizes in May.minimizes in December andJanuary,and shows seasonal variation more remarkable in the SW compared to the eastern part.Inthe SW plateau the total heat is much more intense than the eastern counterpart in all the seasonsexcept winter.Under the effect of the sensible heat,the total heat on the SW plateau starts toconsiderably intensify in February,which leads to a predominant heating region in the west,withits center experiencing a noticeable westward migration early in summer and twice pronouncedweakening in July and after October.However,the weakening courses are owing to differentcauses.The total heat over the north of QXP is greatly strengthened in March.thus generatinganother significant thermal region in the plateau.  相似文献   

祁连山区大坂山隧道围岩的冻融状况分析   总被引：6，自引：5，他引：1  

何春雄  吴紫汪  朱林楠 《冰川冻土》2000,22(2):113-120

通过对严守地区隧道现场基本气象条件的分析,建立了隧道内空气与围岩对流换热及固体导热的综合模型;在隧道内空气以紊流为主的情况下,分析预报了祁连山区大坂山隧道开通运营后洞内温度及围岩冻结、融化状况,并与在隧道内空气以层流为主的情况下的已有结论进行比较。  相似文献