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1.
乔丹 《陕西水利》2016,(5):112-114
水体中溶解氧的含量是表征水体生态功能的重要指标和控制性因素,其主要来源是大气复氧,因此水体大气复氧机理和影响因素是水体生态环境研究的重要课题,目前主要集中于水体大气复氧系数计算方面。本文通过对水体大气复氧系数计算公式的研究进行总结,概括了水体大气复氧系数计算方程的基本形式,并指出了它们的应用条件和存在问题。以期为今后其他学者研究水体大气复氧提供依据。  相似文献   

2.
水体大气复氧理论和复氧系数研究进展与展望   总被引:10,自引:0,他引:10  
雒文生  李莉红  贺涛 《水利学报》2003,34(11):0064-0070
作者对水体大气复氧理论和复氧系数计算公式研究进行总结,分析了水体在静止和紊动水流条件下大气复氧的理论模型和复氧方程,并对计算复氧系数的公式的适用范围进行分析,概括了水体大气复氧方程的基本形式。各复氧系数计算公式大多是基于各自的水力条件,忽略了其他的因素而不能应用于所有的河流,因此可靠性较差,但相对而言,其中以ThackstonKrenkel公式较为有效。  相似文献   

3.
<正> 已有的国内外河流水质模型中,对复氧的计算,只考虑了水气交界面上的大气复氧、光合作用产氧等方面的因素,未计入河渠中因建筑物泄流卷吸空气而产生的复氧作用,从而对复氧和自净能力估计偏低。随着水资源开发的蓬勃发展,在河流上尤其中小型河流或渠道上兴建有相当数量的  相似文献   

4.
水体中的溶解氧是其生态功能的重要控制性因素,主要来源于大气复氧,因此水体大气复氧机理和影响因素是水体生态环境研究的重要课题,目前主要集中于水体大气复氧模型和复氧系数计算方面。通过概括总结水体大气复氧的理论模型及其复氧系数计算方程基本形式,以期为今后其他学者的研究提供依据。  相似文献   

5.
陕西汉江干流有机质环境容量的研究   总被引:2,自引:0,他引:2  
依据水环境功能区划分原则及技术方法对汉江干流地面水域的功能区进行划分。并采用野外观测及实验室分析相结合方法,利用汉江已有的环境观测资料和水文资料确定耗氧系数K1和复氧系数K2值。根据陕西汉江干流实际水文特点,建立了汉江有机质环境容量计算模型,最终对不同频率流量条件下的汉江有机质环境容量进行计算、分析。  相似文献   

6.
紊动水体表面传质系数的实验研究   总被引:3,自引:0,他引:3  
李然  赵文谦  李嘉  李克锋 《水利学报》2000,31(2):0060-0066
本文根据紊动扩散理论及气液界面质量传递过程,提出了紊动水体复氧过程的概化模型。在对紊动水体复氧过程的研究中,采用了将由分子扩散引起的氧传递和由紊动扩散引起的氧传递分别进行研究的新方法。根据在紊动诱发实验装置内进行的大量复氧实验及理论分析,分别确定了无紊动和不同紊动强度下的表面传质系数,并建立了表面传质系数与紊动动能之间的定量关系式。这一关系充分考虑了表面紊动动能对复氧的影响,对于研究紊动复氧水体表面传质系数、复氧过程及水体内溶解氧浓度的分布具有重要意义。  相似文献   

7.
区间运算的保守性问题是困扰区间潮流的主要问题之一。文中将复平面上区间数的3种不同表达方式,即方形域表达、圆盘域表达和扇形域表达引入区间潮流,来研究它们对区间潮流结果保守性的影响。复区间潮流采用的基本算法是配电网前推回推复区间潮流算法。采用33母线系统为算例,对潮流结果的保守性进行了研究,得出结论认为,根据电力系统中负荷的不同基本组成,来选择适当的复区间表示方式,可以降低区间潮流计算结果的保守性。  相似文献   

8.
在用于电力系统关键特征值计算的精化Cayley-Arnoldi算法中,采用精化Ritz对替代原来的Ritz对,从而形成改进型算法。由于精化Ritz向量包含更多的子空间信息,精化Ritz值更接近其最终收敛的Ritz值,改进后的算法更有利于迭代计算的收敛;精化Ritz对能够廉价可靠地求得,计算时间增加有限。算例分析表明,仅需1次Cayley变换即可把复平面特定区域内的特征值转换为主特征值,并能明显区分相近特征值,验证了所提出算法的计算速度和收敛特性。  相似文献   

9.
本文首先通过水槽实验并用数值计算方法求得了潮汐流动复氧系数的瞬时值K_2,潮平均值K_2和相应于稳态模型的等效值〈K_2〉。通过对潮汐流和恒定流复氧系数的比较分析,得出当潮汐加速度很小时,潮汐流动的复氧系数可分时段按恒定流考虑确定。通过对等效复氧系数〈K_2〉的推求,得出了〈K_2〉与潮平均值之间的关系并在一定条件下可用系数φ作为判别〈K_2〉近似于的判据。最后还将实验研究所得成果应用于珠江广州河段,得到天然观测值的良好验证。  相似文献   

10.
城市河道水体复氧修复的水力学方法研究   总被引:2,自引:0,他引:2  
目前,我国城市河流已不同程度受到污染,河道曝气复氧对消除水体黑臭的良好效果,已被实验室试验与河道曝气试验所证实。通过分析几种典型的城市河道水体复氧修复的水力学方法,提出根据河流不同的特点.采用不同形式水工建筑物、水土建筑物进行溢流坝面加糙、接触氧化透水堤、跌水曝气充氧等水力学方法对城市河道水体进行复氧修复。  相似文献   

11.
1 . INTRODUCTIONWiththedevelopmentofeconomy ,waterpol lutionbecomesratherserious .ThecontentofDOinwater ,whichisreaerationoccurringattheair watersurfaces ,isanimportantindexofwaterquality .DOcanbalancethewaterecologyandde composetheorganisminwater .ThelackofDOwillthreatenorganisminwater .OncetheDOisdepletedout,organismwilldecomposeinanaero bicconditionandwaterwillturnsmell.Theturbulentdiffusionandtransferofpollu tantinwatermaydilutetheconcentrationofthepollution ,anddecomposedcontamin…  相似文献   

12.
This paper is concerned with theoretical and experimental study on theconical swirling water jet flow.Based upon the theoretical analysis,the experiment on thestructural characteristics of swirling water jet flow including the velocity and pressure dis-tribution laws,on which the parameters of the jet,nozzle and directional blades havemore or less influence,was carried out in CSSRC by using a 3-D LDV in order to optimizea new high-efficiency jet instead of swirling drilling bit for rock-breaking and continuouslydrilling,and to meet the demand of radial horizontal drilling technology.Meanwhile basedon the experimental results,the numerical simulation was conducted for the conicalswirling water jet in the immersed well-bottom flow by solving the RANS equations in the3-D body-fitted coordinate system with the k-ε turbulence model.The numerical resultsare consistent with the experimental data,and lead to some conclusions which are impor-tant for applying the conical swirling water jet to the petroleum drill  相似文献   

13.
A numerical model of transverse mixing in natural rivers has been presented byusing the body-fitted coordinate systems,which is capable of describing the complex flow andmixing characteristics of rivers.To study the validity and to illustrate the applicability of thismodel,field measurement date in the Gan River near Nanchang have been used to compare thenumerical results.  相似文献   

14.
NUMERICAL PREDICTION OF VORTEX FLOW IN HYDRAULIC TURBINE DRAFT TUBE FOR LES   总被引:12,自引:8,他引:4  
The three-dimensional unsteady turbulent flow is studied numerically in the whole flow passage of hydraulic turbine, and vortex flow in the draft tube is predicted accurately in this paper. The numerical prediction is based on the Navier-Stokes equations and Large-Eddy Simulation (LES) model. The SIMPLE algorithm with the body fitted coordinate and tetrahedroid grid system is applied for the solution of the discretization governing equations.  相似文献   

15.
由于游荡型河道河岸变形尺度远小于河宽尺度,给计算带来了不便。通过讨论在正交曲线贴体坐标下建立平面二维水沙数学模型,以实例进行模拟分析,引入移动坐标技术,使得计算区域的网格随河岸后退而移动,从而可以较好地解决河岸变形尺度与河岸尺度不匹配的问题。  相似文献   

16.
引入自适应网格技术,建立了曲线坐标系下考虑能耗影响的缓变水深水域波浪传播的数值模拟模型,通过在模型中引入能量耗散项以更好地处理全透射边界。基于原型缓坡方程,完善了等水深的轴对称双导堤水域内波浪传播的精确解表达式及其计算结果;提供了等水深的环形河道水域内较为详细的精确解。在极坐标系下就等水深的轴对称双导堤水域内波浪的传播,推导了缓坡方程的小角度抛物近似模型的解析解表达式。就上述两水域内波浪传播的数值模拟模型的数值解、抛物近似模型的解、精确解进行了详细比较,说明数值解与精确解相吻合、数值模拟模型比小角度和大角度抛物近似模型具有更高的精度。数值模拟模型能较好地模拟水深复杂变化的地形上波浪的传播,能有效反映波浪传播过程中的多种物理现象。  相似文献   

17.
台风浪对长江口深水航道骤淤的影响研究   总被引:4,自引:0,他引:4  
概述风暴对长江口航槽短期地形变化的影响和研究现状,将缓坡方程、Boussinesq方程和动谱平衡方程进行分析比较,选择后者做为长江口台风浪数值预报模式。介绍球坐标下动谱平衡方程模型及方程右端源汇项的处理方法,以9912号台风对波浪数值模型进行验证。数值预报EES向20m/s风场下深水航道水域波浪要素:有效波高分布和波浪水质点底部轨迹运动速度分布。由泥沙起动底流速公式得到深水航道水域底沙起动底流速场,根据长江口波浪水质点底部轨迹运动速度的均方根值与泥沙的起动底流速之差的分布场进行骤淤机理分析。结果表明在EES向20m/s风场作用下横沙浅滩和九段沙浅滩的大部分水域底部泥沙将被掀扬至水体,部分泥沙在跨槽水流带动下会进入航道而造成严重淤积。最后提出研究长江口深水航道风暴骤淤问题的进一步工作。  相似文献   

18.
Recent research on short-term topographic change in the Yangtze Estuary channel under storm surge conditions is briefly summarized. The mild-slope, Boussinesq and action balance equations are compared and analyzed. The action balance equation, SWAN, was used as a wave numerical model to forecast strong storm waves in the Yangtze Estuary. The spherical coordinate system and source terms used in the equation are described in this paper. The significant wave height and the wave orbital motion velocity near the bottom of the channel during 20 m/s winds in the EES direction were simulated, and the model was calibrated with observation data of winds and waves generated by Tropical Cyclone 9912. The distribution of critical velocity for incipient motion along the bottom was computed according to the threshold velocity formula for bottom sediment. The mechanism of rapid deposition is analyzed based on the difference between the root-mean-square value of the near-bottom wave orbital motion velocity and the bottom critical tractive velocity. The results show that a large amount of bottom sediments from Hengsha Shoal and Jiuduan Shoal are lifted into the water body when 20 m/s wind is blowing in the EES direction. Some of the sediments may enter the channel with the cross-channel current, causing serious rapid deposition. Finally, the tendency of the storm to induce rapid deposition in the Yangtze Estuary channel zone is analyzed.  相似文献   

19.
1 . INTRODUCTIONThevalvehasbeenplayinganimportantroleinthe pipeengineeringandisalsooneofmaincomponentsgeneratingtheheadloss .Becauseofthecomplexgeometry ,thedesignwasusuallyeval uatedempiricallyinthepast,whichcausesmuchenergyloss .Toreducetheenergyloss ,itisessen tialforadesignertoknowthedetailsofflowfieldinthevalvepipe .Recently ,withtheremarkableprogressintheComputationalFluidDynamics(CFD)andcomputerhardware ,itisexpectedthatCFDwillbecomeapowerfultoolinthedesignofvalve .Intheactual…  相似文献   

20.
Based on the characteristics of backflow,a two-dimensional mathematical model of sediment movement was established.The complexity of the watercourse boundary at the confluence of the main stream and the tributary was dealt with using a boundary-fitting orthogonal coordinate system.The basic equation of the two-dimensional total sediment load model,the numerical calculation format,and key problems associated with using the orthogonal curvilinear coordinate system were discussed.Water and sediment flow in the Chongqing reach of the Yangtze River were simulated.The calculated water level,flow velocity distribution,amount of silting and scouring,and alluvial distribution are found to be in agreement with the measured data,which indicates that the numerical model and calculation method are reasonable.The model can be used for calculation of flow in a relatively complicated river network.  相似文献   

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