Mechanisms for the link between onset and duration of open water in the Kara Sea

The sea ice conditions in the Kara Sea have important impacts on Arctic shipping,oil and gas production,and marine environmental changes.In this study,sea ice coverage(C_(R))less than 30%is considered as open water,its onset and end dates are defined as T_(open)and T_(close),respectively.The sea ice melt onset(T_(melt))is defined as the date when ice-sea freshwater flux initially changes from ice into the ocean.Satellite-based sea ice concentration(SIC)from 1989 to 2019 shows a negative correlation between T_(open)and T_(close)(r=-0.77,p<0.01)in the Kara Sea.This phenomenon is also obtained through analyzing the hindcast simulation from 1994 to 2015 by a coupled ocean and sea-ice model(NAPA1/4).The model results reveal that thermodynamics dominate the sea ice variations,and ice basal melt is greater than the ice surface melt.Heat budget estimation suggests that the heat flux is significant correlated with T_(open)(r=-0.95,p<0.01)during the melt period(the duration of multi-year averaged T_(melt)to T_(open))influenced by the sea ice conditions.Additionally,this heat flux is also suggested to dominate the interannual variation of the heat input during the whole heat absorption process(r=0.81,p<0.01).The more heat input during this process leads to later T_(close)(r=0.77,p<0.01).This is the physical basis of the negative correlation between T_(open)and T_(close).Therefore,the duration of open water can be predicted by T_(open)and thence support earlier planning of marine activities.

Effect of Time Step Size and Turbulence Model on the Open Water Hydrodynamic Performance Prediction of Contra-Rotating Propellers

A growing interest has been devoted to the contra-rotating propellers （CRPs） due to their high propulsive efficiency, torque balance, low fuel consumption, low cavitations, low noise performance and low hull vibration. Compared with the single-screw system, it is more difficult for the open water performance prediction because forward and aft propellers interact with each other and generate a more complicated flow field around the CRPs system. The current work focuses on the open water performance prediction of contra-rotating propellers by RANS and sliding mesh method considering the effect of computational time step size and turbulence model. The validation study has been performed on two sets of contra-rotating propellers developed by David W Taylor Naval Ship R ＆ D center. Compared with the experimental data, it shows that RANS with sliding mesh method and SST k-ω turbulence model has a good precision in the open water performance prediction of contra-rotating propellers, and small time step size can improve the level of accuracy for CRPs with the same blade number of forward and aft propellers, while a relatively large time step size is a better choice for CRPs with different blade numbers.

Applying Periodic Boundary Conditions to Predict Open Water Propeller Performance

Mathematical models of propellers were created that investigate the influence of periodic boundary conditions on predictions of a propeller's performance.Thrust and torque coefficients corresponding to different advance coefficients of DTMB 4119, 4382, and 4384 propellers were calculated.The pressure coefficient distribution of the DTMB 4119 propeller at different sections was also physically tested.Comparisons indicated good agreement between the results of experiments and the simulation.It showed that the periodic boundary condition can be used to rationally predict the open water performance of a propeller.By analyzing the three established modes for the computation, it was shown that using the spline curve method to divide the grids can meet the calculation's demands for precision better than using the rake cutting method.

Greenhouse Gas Emission from Inland Open Water Bodies and Their Estimation Process—An Emerging Issue in the Era of Climate Change

The persistent rise in concentrations of greenhouse gases (GHGs) in the earth’s atmosphere is responsible for global warming and climate change. Besides the known source of GHGs emissions like energy, industry, and agriculture, intrinsic emissions from natural inland water bodies like wetland, rivers, reservoirs, estuaries, etc. have also been identified as other hotspots of GHGs emission and gaining the attention of the scientific communities in recent times. Inland fisheries in India are threatened by climate changes such as a change in temperature, precipitation, droughts, storm, sea-level rise, saltwater intrusion, floods that affect mostly the production, productivity and ultimately affect the fishers’ livelihood. There are, however, different mitigation and adaptation strategies to cope with the effects of climate change. Carbon sequestration and other related management interventions are one of the options available minimizing GHGs emissions from inland open waters, particularly the wetlands and coastal mangroves which are well known worldwide for their significant role in the storage of carbon. Assessment of C efflux from exposed sediments in dry streams, reservoirs, lakes, rivers, and ponds into the atmosphere can be considered imperative for a better understanding of their role as a C-sink or as a C-source to the atmosphere.

Surface Water Quality Profiling Using Physicochemical Parameters in Open Defecation Free and Non-Open Defecation Free Local Government Areas in Benue State, Nigeria

Physicochemical parameters of surface water sources in the study of local government areas (LGAs) were assessed using standard procedures. The mean physicochemical parameters for pH (5.49), NO2 (0.23 mg/L), SO4 (0.77 mg/L), Na (28.72 mg/L), Ca (28.94 mg/L), Mg (17.50 mg/L), Cl (11.65 mg/L), TSS (6.27 mg/L), TDS (104.23 mg/L), BOD (2.83 mg/L) and F (0.87 mg/L) were below WHO standards irrespective of their defecation status. The values for electrical conductivity (EC) (2770.50 µs/cm, turbidity (481.24 NTU), dissolved oxygen (DO) (5.32 mg/L), chemical oxygen demand (COD) (445.50 mg/L), K (125.06 mg/L), PO4 (0.78 mg/L) and Fe (0.57 mg/L) were above the WHO limits for safe water. Higher EC and COD values obtained in the study is evidence of pollution of the water sources by organic matter.

Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean

Estimates of the surface heat budget over drifting ice and open water in the Arctic Ocean are made using eddy correlation and flux-profile methods using data obtained from drifting ice and from the R/V Xuelong in the Chinese National Arctic Research Expedition during August 19—24,1999. The results show that the net radiation received by the ice surface is mainly lost through the sensible heat flux and the heat flux due to melting ice, and the latent heat flux making small contribution to the heat balance. However, the heat balance of the open water surface was dominated by the radiative flux whereas the latent and sensible heat fluxes and the oceanic heat flux were greater than those on the sea-ice surface. These results emphasize that thermodynamic processes are quite different between air/open water and air/sea-ice over the Arctic Ocean which is important when considering the effect of sea-air-ice interaction on climate change process dur-ing the summer period.

Study on numerical simulation to water lowering in an open coal mine digging

In view of the situation of excavation of should carry out simulation studies for the numerical open coal mine for the underground water disaster, we value of the water lowering project and improve the accuracy and the level of the water lowering project. On the basis of the hydrological geological conditions of certain open mine digging, a more reasonable seepage numerical model was built according to MODFLOW. It was simulated in advance that the process of the confined water level descending with the time, and combining with the actual observations to test the correctness of the model. The calculation showed that the results coincided well with the results of actual measurement. Based on this, different water lowering numerical simulations were built for the open coal mine digging. It could be simulated and forecast that the changes of the groundwater level in drainage process within and outside the mine pit, and it was quantitatively assessed that the possible water lowering result of the opencast water drainage process, which provide an important basis for the actual water lowering project and the possible project disposal.

CAS center for water resources opens in Beijing

The CAS Water Resources Research Center (WRRC) has recently been established in Beijing. Its opening ceremony was held on 3 December, 2006, at

偏转工况L型吊舱推进器敞水性能数值研究

针对吊舱推进器在偏转时诱发的剧烈的水动力不稳定问题,以某L型吊舱推进器为研究对象,采用计算流体力学(CFD)方法和滑移网格技术对不同偏转角β(β=0°、±10°、±20°、±30°)下L型吊舱推进器进行敞水性能数值研究。研究结果表明:吊舱推进器螺旋桨的推力、扭矩以及吊舱单元的侧向力均随偏转角的增大而变大,其中吊舱推进器螺旋桨的推力系数、扭矩系数受偏转方向影响较小。β=0°时,受螺旋桨旋转时产生的周向诱导速度的影响,吊舱推进器在直航工况下也会受到侧向力作用,当吊舱推进器向右偏转时,其迎流侧产生的侧向力会与螺旋桨旋转尾流产生的侧向力相互抵消,导致吊舱推进器在向右偏转时产生的侧向力整体小于向左偏转时产生的侧向力;由于螺旋桨旋转尾流会与后方舱体、支架相互干扰,吊舱推进器整体推力系数并不是关于直航时对称,小偏转角(|β|≤15°)对吊舱推进器整体的推力系数影响较小,当偏转角|β|>15°时,推力系数会迅速下降。

几何参数对轮缘推进器水动力性能影响的研究

轮缘推进器是近年来发展起来的一种无轴组合式特种推进器。与传统推进器相比,轮缘推进器在水动力设计和性能分析方面存在诸多挑战,水动力性能的研究对轮缘推力器的设计和应用具有重要意义。为了研究几何参数对轮缘推力器水动力性能的影响,本文以7叶轮缘驱动推力器为基本模型,基于面元法原理,利用编译的面元法代码对轮缘推力器在开阔水域的工作状态进行了数值模拟。通过求解每个面元的速度场,计算了水动力性能和叶片表面压力分布。此外,本文选择了几个典型的几何特征,如螺距比和叶片数,通过进行变参数分析,比较了不同几何参数下轮缘推力器的敞水性能。结果表明:本文的相关研究对轮缘推力器的设计和开发具有参考价值。

导管螺旋桨水动力性能试验及数值研究

为了研究导管螺旋桨的推力、扭矩和敞水效率等主要水动力参数和进速系数之间的关系,本文采用物理模型试验和计算流体力学(Computational Fluid Dynamics,CFD)技术相结合的方式分析导管对螺旋桨水动力特性的影响。首先在本校拖曳水池开展导管螺旋桨模型的敞水性能试验然后使用计算流体软件STAR-CCM+对导管桨模型进行数值模拟。在模拟计算中应用多参考系法(Multi Reference Frames,MRF),分别采用不同湍流模型对导管螺旋桨的水动力性能进行计算,并与试验数据进行对比,验证了STAR-CCM+软件模拟可以对导管螺旋桨的水动力性能进行有效预报且使用SST k-ω湍流模型获得的水动力性能精度更高。研究结果表明,导管螺旋桨更适用于在低进速系数下工作的重载船舶。

基于过热蒸汽干燥开式制粉燃褐煤发电技术研究

针对高水分褐煤燃烧发电中存在的热效率低和低负荷稳燃困难等问题,提出了基于过热蒸汽干燥开式制粉系统的新型高效燃褐煤发电技术,该技术采用基于汽轮机抽汽加热的过热蒸汽干燥开式制粉系统,保证了制粉系统的运行安全性,提高了燃烧系统的运行灵活性,实现了制粉系统与锅炉主机的运行解耦,并综合解决了褐煤锅炉炉温低、热效率低的等问题。以600 MW超临界燃褐煤机组为例,对采用该技术的热力系统进行了仿真,分析了其节能与环保效益。研究结果表明,该技术通过对锅炉与汽轮机整体热力系统的综合优化,将汽轮机回热系统扩大至高水分煤的干燥过程,同时梯级回收锅炉排烟废热和制粉乏汽废热至汽轮机回热系统,可获得较为显著的节煤效益。同时,该技术不仅可由节煤相应减少各类污染物及CO_(2)排放,还可回收大量水资源,有望实现零水耗电厂。

Determination of optimal grid opening width for herringbone water-sediment separation structures based on sediment separation efficiency

The herringbone water-sediment separation structure(HWSSS) was developed to prevent debris flows. This paper mainly focuses on evaluating the sediment separation efficiency of HWSSS in debris flow prevention and determining the grid opening width D, a crucial structure parameter for HWSSS design. Theoretical analysis on the total sediment separation rate Pt reveals that the efficiency of sediment separation is much related with sediment grain size distribution(GSD) and grid opening width. The lower limit of Pt is deduced from the perspective of safety consideration by transforming debris flow into sediment-laden flow. Hydraulic model tests were carried out. Based on the regression analysis of the experimental data, the quantitative relationships between Pt and D and GSD characteristic values were finally established. A procedure for determining optimal grid opening width is proposed based on these analyses. These results are of significance in evaluating sediment separation effect by HWSSS in debris flow prevention and contribute to a more explicit methodology for design of HWSSS.

重型破冰船多桨状态对敞水性能的影响分析

针对重型破冰船敞水与破冰2种典型工况阻力差距巨大,而螺旋桨设计基准为破冰工况,研究如何处理重型破冰船敞水航行时三桨工作状态对于降低能耗具有重要意义。以系柱状态模拟破冰工况对三桨重型破冰船的螺旋桨进行设计并进行空泡校核修正,针对三桨推进、中间桨闲置舷侧两桨推进、舷侧两桨闲置中间桨推进3种不同工作状态下的敞水航行性能进行估算,对比分析得出三桨降功率敞水推进相对于闲置螺旋桨推进更有利于降低总推进功率并满足敞水设计航速要求。

半夏泻心汤对功能性消化不良大鼠抑郁状态及促肾上腺皮质激素释放因子相关通路的影响

目的:观察半夏泻心汤对功能性消化不良(FD)大鼠抑郁样行为、下丘脑促肾上腺皮质激素释放因子(CRF)及其受体CRF-R1、CRF-R2的影响。方法:48只SPF级Wistar大鼠随机分为空白组、模型组、氟西汀组、半夏泻心汤低、中、高剂量组,共六组,每组各8只。空白组正常饲养,其余五组采用不规则喂养+夹尾激惹刺激法造模,造模成功后半夏泻心汤低、中、高各剂量组分别给予0.62、1.24、2.48 g/ml剂量灌胃,氟西汀组给予2 mg/kg氟西汀,空白组及模型组均给予同等容积的蒸馏水,各组连续灌胃14 d。干预结束后采用糖水偏好实验和旷场实验测试各组抑郁样行为;HE染色观察大鼠胃窦组织基本形态;RT-qPCR和Western blot检测大鼠下丘脑中CRF、CRF-R1和CRF-R2 mRNA和蛋白的表达。结果:与空白组比较,模型组大鼠体重、糖水偏好度、旷场实验移动总距离和直立次数均明显下降(P<0.05);下丘脑中CRF、CRF-R1 mRNA和蛋白表达均明显升高(P<0.01),CRF-R2 mRNA和蛋白的表达均明显降低(P<0.01)。与模型组比较,半夏泻心汤各剂量组大鼠的体重、糖水偏好度、旷场实验移动总距离和直立次数均明显增加(P<0.05);半夏泻心汤各剂量组FD大鼠下丘脑中CRF、CRF-R1 mRNA的表达量均明显降低(P<0.01),CRF-R2 mRNA的表达明显升高;半夏泻心汤高剂量组FD大鼠下丘脑中CRF蛋白表达均明显降低(P<0.01),半夏泻心汤各剂量组FD大鼠下丘脑中CRF-R1蛋白表达明显降低(P<0.01),CRF-R2蛋白表达升高(P<0.05)。结论:半夏泻心汤可通过调控CRF通路,恢复CRF-R1和CRF-R2的平衡状态,发挥抗抑郁的作用。

有机玻璃管道直接水锤压力特性试验研究

为了了解黏弹性管道的水锤压力特性,文中通过搭建水库-管道-阀门系统模型,进行了系列关阀水锤试验,针对有机玻璃管道中末端阀门初始开度分别为30%,100%时关阀产生的直接水锤压力变化规律进行了研究,从黏弹性材料的本构关系角度分析了关阀时间对黏弹性材料直接水锤的影响机理,并对2种不同初始开度下阀门附近的流场进行了三维数值模拟.研究结果表明:黏弹性管道中直接水锤压力变化规律与传统的水锤理论不符,直接水锤压力不仅与阀门的关闭时间有关,还与阀门的初始开度有关,满足“阀门关闭越快,直接水锤压力越大”与“阀门初始开度越小,直接水锤压力越大”的规律.

一种改进诱导因子计算方法的叶素动量理论体积力模型

叶素动量理论体积力模型作为能够替代真实螺旋桨的一种体积力形式,在模拟螺旋桨以及船桨相互作用问题中具有较大的应用潜力。为了处理基于理想流体假设的传统叶素动量理论在与粘性求解器耦合过程中不能在较大工况范围内准确代表真实螺旋桨模型的问题,本文提出一种基于真实螺旋桨诱导因子分布的改进方法,并进行KP505螺旋桨体积力模型在J=0.4~0.8五种进速条件下的敞水试验模拟。本文将敞水性能、桨载荷分布与诱导速度场的体积力模拟结果与真实螺旋桨模型进行了对比,结果表明改进后的体积力模型预报敞水性能误差在各进速下最大值为1.05%,且体积力模型诱导速度场可以反映真实螺旋桨尾流的动量输运。

城市人工浅水湖泊底栖动物群落结构及影响因素分析

探讨梅溪湖底栖动物群落结构及其影响因素,为城市人工湖泊水生态系统修复后的运营维护管理提供理论依据。2020-2021年在梅溪湖设置14个采样站位(敞水区7个,滨岸带7个),按季节开展底栖动物调查。研究结果表明,梅溪湖底栖动物种类达75种,滨岸带种类数高于敞水区。整个湖区全年优势种为米虾(Caridina sp.)、铜锈环棱螺(Bellamya aeruginosa)、椭圆萝卜螺(Radix swinhoei)、大脐圆扁螺(Hippeutis umbilicalis)、霍甫水丝蚓(Limnodri-lus hoffmeisteri)和沼虾(Macrobrachium sp.)。敞水区和滨岸带群落结构存在显著差异,除霍甫水丝蚓外,全年优势种是导致2个区域群落结构差异的主要分类单元。梅溪湖底栖动物现存量和多样性季节间无显著差异,但敞水区和滨岸带之间差异显著,滨岸带远高于敞水区,表明水生植物群落的构建有利于底栖动物种群的壮大和多样性的提高。CCA结果表明,氨氮(AN)和营养水平(TLI)对敞水区和滨岸带的底栖动物群落结构均有较大影响。CoIA分析结果显示,米虾、大脐圆扁螺、铜锈环棱螺、沼虾、椭圆萝卜螺等物种与环境因子存在较为密切的联系,这些物种可以作为梅溪湖水环境条件变化的指示种。合理控制梅溪湖底栖动物群落结构,并维持较高的多样性水平,可有效促进其生态系统的正常运转。

基于双调和样条插值和量纲分析的过闸流量计算

过闸流量的精确计算是保障调水工程安全运行的基础,过闸流量计算模型是数字孪生调水工程建设的重要水力模型之一。调度运行中虽积累大量的实时水情数据,但受控制模式和用水需求等因素的影响,实际监测数据多集中于少量的局部范围内,难以获得覆盖范围广且具有代表性的数据,导致过闸流量模型的泛化能力不足。针对上述问题,提出了一种双调和样条插值和量纲分析的过闸流量计算方法,在样本点较少的实际情况下,通过充分利用样本点的位置信息进行数据插补后,利用量纲分析法进行过闸流量计算。以南水北调中线工程岗头节制闸和西黑山节制闸为研究对象,对比分析双调和样条插值和量纲分析方法与单一量纲分析法在过闸流量计算中实测样本与拟合曲线的决定系数、计算精度等。结果表明,相比于单一量纲分析法,在代表性数据缺乏的条件下,基于双调和样条插值和量纲分析的弧形闸门过闸流量计算方法具有较高的计算精度,过闸关系曲线拟合决定系数约提高8%,过闸流量计算结果的绝对误差和相对误差都有所降低。

三门峡水库控制运用方式的优化探讨

三门峡水库“蓄清排浑”运用为多沙河流的治理提供了宝贵经验,随着来水来沙情况的变化及对水库功能需求和对水库泥沙冲淤规律认识的深化,该运行方式亦在实践中不断调整和完善。为此,针对不同的典型年份设定集中敞泄与分段敞泄的敞泄排沙方案,采用一维非恒定水沙数学模型,对选取的2018~2019年丰水少沙年和2014~2016年枯水少沙年设定12种控制运用方案进行模拟,比较各方案下库区冲淤变化的优劣,据此选取适合三门峡水库的控制运用方式。结果表明,2018~2019年分段敞泄方案的冲刷效果优于集中敞泄方案,即使在后汛期的控制水位抬高至310 m,也能达到较好的冲刷效果;2014~2016年分段敞泄方案虽优于集中敞泄方案,但其冲刷主要集中于2014年汛期,2015、2016年整体呈淤积状态,综合考虑建议枯水少沙年份水库采用“泥沙年际调节”运用模式。